PorràThe remains of a Punic necropolis discovered during construction work in Sardinia construction workers unearthed an amphora — a tall jar with two handles and a narrow neck — and immediately reported the discovery to the archaeologist supervising the site A team of researchers promptly flocked to the area and further excavations revealed five more amphorae At least some of them contained human remains likely belonging to children The discovery dates back to the third or fourth century B.C.E. While the full extent of the necropolis may never be revealed due to the heavy concentration of structures nearby experts hope to learn as much as they can about the people who lived and died in the area more than 2,400 years ago construction workers were beginning a project to install a gas line alongside a busy road in Sestu when they dug up an amphora containing human bones They immediately turned off their bulldozer and alerted the supervising archaeologist who brought in additional experts to investigate five additional amphorae have been recovered The excavation is led by Enrico Trudu from the Archaeological Superintendence of Cagliari who specializes in the Phoenician-Punic era PorràOne of the amphorae unearthed during excavations Speaking to L’Unione Sarda “We are still in the excavation phase but I can confirm that in several places contexts have emerged that can clearly be ascribed to a Punic necropolis.” Trudu explained that the six amphorae were “enchytrismos” burials a method commonly seen in Punic settlements — and they likely held the bones of infants or young children a sort of coffin that could contain both children’s and adults’ bodies,” Trudu told L’Unione Sarda “In some of those we recovered there were human bones bones that were also found in various places around There is no doubt that the context is funerary There is also a pit that we are going to investigate as we are working along the entire trench starting from the most exposed points that we will then expand.” archaeologists unearthed a trove of Punic artifacts Given the new breadth of the archaeological project Trudu said it is likely that his team will find even more ancient relics buried along the trench the scope of the excavation will remain limited “It will be impossible to investigate the entire necropolis,” Trudu added “but it is important to analyze and secure the parts and finds that have come to light also to have an idea of what could be found in the case of future public works.” this discovery could help shine a new light on Phoenician-Punic Sardinia Around the time this necropolis was created parts of Sardinia were under the control of Carthaginians from North Africa who would have brought these burial practices with them PorràThe busy street where the necropolis was found Punic Sardinia was an incredibly important Carthaginian province playing a major role in Mediterranean politics made it a prime target during the Punic Wars which resulted in Rome conquering Sardinia in 238 B.C.E The defeat marked the end of the Phoenician-Punic era on the island but these amphorae are now revealing more about the daily life and funerary practices of the long-lost culture After reading about the Punic necropolis discovered in Sardinia, learn about Tyrian purple, a vibrant dye created by the Phoenicians. Or, go inside the bizarre story of casu marzu the traditional Sardinian cheese filled with live maggots All is set for an Elective Conference by Secondary School Teachers Union (SESTU) from 21st to 22nd August Delegates from all education districts in all education divisions across the country will come to cast their votes Druwen Frank Moyo who is being challenged by Christopher Chitsumba and Mthana Dzonzi says the union is ready for this important exercise There is an independent body that will run everything on this day,” said Moyo told Nyasa Times that everything is in place to ensure free and fair elections Said Mbano:“Contestants are coming from all the divisions and they are registered members of SESTU I can say the ground is level and we have tried as much as possible to encourage women to contest in different positions Elections will be done in an open hall and we are sure that they will be free and fair.” Current president Pilirani Kapolo from Central West Education Division is being challenged by Kingdom Chipaza from South West Education Division Judith Kamkwamba from South West Education Division is being challenged by Humphrey Smart Mathewe from Shire Highlands Education Division on the position of Treasurer General Druwen Frank Moyo thinks the current executive has done a good job so far on interim basis “I think we have done well so far as a mouth piece for all secondary school teachers in the country SESTU has worked hard to take teachers’ concerns and challenges to different stakeholders We have challenged bad polices by MANEB and other issues We also pushed for promotions of secondary schools and many have been promoted now but we need more promotions for some more teachers,” explained Moyo Secondary School Teachers Union (SESTU) was registered on 5th August The Lilongwe University of Agriculture and Natural Resources (LUANAR) has entered into partnership with Zimbabwe’s Midlands State University (MSU) through.. The Secondary School Teachers Union (SESTU) elective conference that took place at Lilongwe Girls Secondary School on Wednesday saw Pilirani Kapolo Druwen Frank Moyo and Judith Charity Kankwamba retaining their positions as President Pilirani Kapolo from Central West Education Division floored Kingdom Chipaza from South West Education Division on the position of President while Druwen Frank Moyo from the Northern Education Division overcame Christopher Chitsumba and Mthana Dzonzi on the position of General Secretary Humphrey Smart Mathewe from Shire Highlands Education Division lost to Judith Kamkwamba from South West Education Division on the position of Treasurer General Speaking to Nyasa Times after the election President Pilirani Kapolo said delegates wanted someone who cares about their welfare “I and my team have always been with them when they needed our services I led an interim team which served according to their expectations,” said Kapolo Quizzed on what this win means this time around not on interim basis Kapolo said the union now has full bargaining powers “We had challenges presenting issues directly to government negotiating team my team will be presenting issues affecting our members directly to government and this will definitely lead to the improvement of secondary school teachers’ welfare we were not able to participate in negotiations with government because we didn’t have bargaining powers,” he said said he was excited to note that secondary school teachers in the country had trust in him I have learnt that secondary school teachers in Malawi have great trust in me Having amassed the needed bargaining powers as a union we will be able to affiliate with different bigger bodies We will also be able to partner with international organisations.” officials from the Ministry of Labour and other unions were present at the elective conference says it is opposed to the decision by the Government.. The concert (whose Artistic Direction is curated by Maestro Ignazio Perra) is promoted and implemented by the "Ennio Porrino" Musical Cultural Association of Elmas with the implementation collaboration of Art & Show srl the oldest instrument of Sardinian popular music whose origins date back to prehistoric times the new concert production of the “Ennio Porrino” Musical Cultural Association of Elmas begins With "Sonus antigus de Sardigna" it was decided to create a musical path characterized by the performance of pieces belonging to the repertoire of the Sardinian tradition also proposed in comparative form with the performance of modern and contemporary pieces the instrumental vocal concert "Sonus antigus de Sardigna" will be held in Sestu (at the NS delle Grazie Church) which will feature the Cuncordia group in Launeddas (directed by Maestro Gianfranco Meloni) with the participation of Marianna Orrù (mezzo soprano) ) and Pasquale Perra (piano) which in the jargon of launeddas players means playing together identifies an executive proposal that has the intent to give an orchestral breath as broad as possible to the launeddas while not representing a usual model of Sardinian music aims to enhance and further develop the musical potential of launeddas The performance of pieces in a traditional way is presented by the launeddas ensemble in the form of a solo or cuncordia in the traditional sense The concert (whose Artistic Direction is by Maestro Ignazio Perra) is promoted and implemented by the "Ennio Porrino" Cultural Music Association of Elmas with the implementation collaboration of Art & Show srl with the contribution of the Autonomous Region of Sardinia - Department of PI Entertainment and Sport (as part of the "Sounds and Voices for the Island" project and the production distribution and concert circuit that the Association is carrying out in Sardinia in the year 2022) in conjunction with the Eighth Edition of the Event "Attobius Festas e Traditzionis" (organized by the Cultural Association "TAM TAM" of Sestu in collaboration with the Municipality of Sestu) and with the celebrations in honor of Sant'Antonio da Padova (in collaboration with the Parish of NS delle Grazie di Sestu) In a bold move signaling escalating tensions within Malawi’s education sector the Secondary School Teachers Union (SESTU) has issued an ultimatum to the Ministry of Education daring that if government doesn’t respond to them by November 1st they will have no choice but to escalate matters and call for industrial action “We can no longer tolerate this continued neglect of teachers’ welfare and the Ministry must understand that this is not a request We hope the Ministry will take these concerns with the seriousness they deserve to avoid any disruption to the education system and signed by SESTU president Pilirani Kamoyo and Secretary General Druwen Moyo The union’s frustration stems from a series of unresolved issues that have left teachers grappling with financial despair and unfulfilled promises teachers have seen little substantive action to address their dire circumstances and significant resource shortages in schools With the devaluation of the kwacha and soaring inflation eroding already modest salaries educators are calling for immediate redress to restore dignity and support for those shaping Malawi’s future yet we find ourselves in a state of crisis,” stated a SESTU “We can no longer accept the Ministry’s silence on our concerns This is not just a request; it’s a demand for justice.” Among the union’s key grievances are the unfulfilled promises of promotion letters and overdue salary adjustments that were expected by June 2024 Many teachers remain stuck in lower grades while deserving colleagues are left waiting for recognition and advancement The call for action highlights the stark reality facing educators including skipped salaries and stagnation that has seen some teachers trapped in the same grade for over 25 years The union is also voicing concern over inadequate funding for schools which has severely impacted educational delivery and outcomes SESTU warns that failure to address these pressing issues could lead to disruptions in the education system with industrial action looming on the horizon The union’s leaders emphasize that time is of the essence urging the Ministry to take swift and meaningful action to avert a crisis that could have far-reaching consequences for Malawi’s future all eyes will be on the Ministry of Education to see if they can respond adequately to the urgent needs of the country’s dedicated educators The Malawi Supreme Court of Appeal Judge Justice Dorothy Nyakaunda Kamanga has found private practice lawyer Alexious Kamangila guilty of.. Secondary School Teachers Union (SESTU) says it is deeply concerned and dismayed with the current practices and decisions by the Malawi National Examinations Board (MANEB) regarding the allocation and remuneration of teachers involved in the administration of national examinations In the letter signed by President Pilirani Kapolo and General Secretary Druwen Frank Moyo and made available to Nyasa Times the union argues that teachers have endured systemic neglect and abuse for far too long and it is imperative that this cycle is broken we are deeply troubled by the decision to allocate supervisors and invigilators on a commuting basis instead of providing residential arrangements This decision blatantly ignores the significant transport challenges faced across the country Despite our prior advice and numerous appeals to MANEB to reconsider this arrangement our concerns have consistently fallen on deaf ears,” explains Moyo And reacting to news that MANEB will pay allowances for the main papers at MSCE Examinations in instalments Moyo said this is uncalled for and unacceptable “The issue of paying allowances in instalments is unacceptable It is inconceivable how MANEB expects teachers to effectively perform their duties when they are not fully compensated for their work upfront This delay in payment is not only a financial burden but also demoralising We urge MANEB to expedite the payment of the remaining balances before the end of this week Failure to do so will leave the union with no choice but to mandate our members to cease administering examinations,” added Moyo The union has strongly requested MANEB to convene a meeting with it before marking of JCE and MSCE examinations to address and resolve logistical issues in advance saying should MANEB fail to arrange the meeting SESTU will be compelled to instruct teachers across Malawi to abstain from participating in marking of the examinations this year Moyo went on to dispute the fact that MSCE Examinations have started on a god note as purported by government recently “We earlier said we are administering these examinations under protest because we have outstanding issues with MANEB It is not true that examinations have started on a good note Government should not look at the candidates’ side alone It should also look at the administration side,” lamented Moyo “We trust that MANEB will take these matters seriously and act swiftly to rectify these issues The well-being and fair treatment of our teachers are paramount and we expect immediate and meaningful action from MANEB to address our concerns,” reads the concluding part of the letter President Lazarus Chakwera will tomorrow preside over the opening of the Southern African Confederation of Agricultural Unions (SACAU) Annual Conference.. Sign up for our daily Newsletter and stay up to date with all the latest news You are receiving this pop-up because this is the first time you are visiting our site You are using software which is blocking our advertisements (adblocker) we are relying on revenues from our banners So please disable your adblocker and reload the page to continue using this site.Thanks The Italian company Assomech has developed a processing line for L'Ortolano di Sestu (Cagliari Italy) that allows celery to be processed with fewer workers but with higher yields "The Sardinian company contacted us through their director Salvatore Pisanu," explains Peter Calisesi "because they wanted to improve their yields when processing celery We evaluated their request and then produced a customized line." It is currently built with a specific length but it can be extended as production increases it is possible to automate two types of cuts which is then placed in the tray and filmed "The production line allows the customer to automatically select the desired cut while also recovering waste and washing and draining the product directly as part of the process A fast-bagging system at the end facilitates the operators and improves the efficiency and quality of the finished product." "would like to express our gratitude to Salvatore Pisanu and all the staff for the trust they have placed in us and the excellent collaboration that has been created When technology facilitates the work of companies it ultimately benefits the entire supply chain." For more information: AssomechVia Guido Rossa 7/9 47039Savignano sul Rubicone (FC)Tel.: +39 0541 388060Tel.: +39 391 0909884E-mail: [email protected] FreshPublishers © 2005-2025 HortiDaily.com Retraction Watch Tracking retractions as a window into the scientific process A criminologist whose work has been under scrutiny for a year is set to have a sixth paper retracted Last July, Justin Pickett, of the University of Albany at the State University of New York, posted a 27-page explanation of why he was asking for one of his papers to be retracted. The paper in question had been co-authored by Eric A. Stewart whose work had been questioned by an anonymous correspondent Following pickup of the story by The Chronicle of Higher Education, that paper was eventually retracted, along with four others Stewart co-authored But that was not the end of the tale.  Stewart is now having another paper retracted, this one from 2003 in Justice Quarterly. The paper, titled “School social bonds, school climate, and school misbehavior: A multilevel analysis,” has been cited 186 times according to Clarivate Analytics’ Web of Science Last fall, scientific sleuths Nick Brown and James Heathers analyzed the paper using their RIVETS — for “Rounded Input Variables Exact Test Statistics”: A Technique For Detecting Hand-Calculated Results in Published Research — tool and found a positive result tell us anything definitive about what may have led to it it may be worthwhile to contact the author of the article in question and ask for details of the method used and perhaps also a copy of the data set so that the method can be used to reproduce the published results Pickett wrote to the editors of Justice Quarterly in January of this year saying that the publicly available data Stewart claimed to have used did not match what was reported The editors immediately contacted the publisher and set out to do a thorough and professional investigation They used three outside reviewers who reanalyzed the data I wish all editors and journals were this serious about the validity of what they publish In a June 8 letter to Pickett head of Taylor & Francis’s criminology portfolio The referees found that the article contains numerous errors in the reporting or analyses of the data and they further expressed concern that Dr Stewart was also unable to replicate his analyses the referees questioned the validity of the results reported in the article to reach a conclusion as to whether misconduct occurred We will send the retraction statement to our production team today and they will prepare it for publication shortly window.dojoRequire(["mojo/signup-forms/Loader"] function(L) { L.start({"baseUrl":"mc.us12.list-manage.com","uuid":"4f35c1f2e9acc58eee0811e78","lid":"a15d7de264","uniqueMethods":true}) }) I hope that I am allowed to post a link to our RIVETS preprint here: https://psyarxiv.com/ctu9z/ I thought of the principle behind RIVETS some while back but as far as I know it’s the first time that anyone has used the principle of reported statistics *not* suffering from rounding error to identify problems in a published article It has some faint echoes of John Carlisle’s test for implausibly small baseline difference in RCTs I see there already was a link in the article I’m no statistician but I find that a fascinating idea I’m curious if any more papers have been flagged by your RIVETS This site uses Akismet to reduce spam. Learn how your comment data is processed. Secondary School Teachers Union (SESTU) says this year’s supervisors and invigilators for the Junior Certificate of Education (JCE) Examinations are working under protest as the Malawi National Examinations Board (MANEB) has prepared “meaningless” allowances for them Nyasa Times understands that SESTU wrote MANEB making a number of recommendations based on the circular that the latter released containing reforms in administration of national examinations this year One crucial observation that SESTU made was about the residential/commuter ratio policy which it said was unrealistic because Malawi as a nation has different areas with different physical terrain told Nyasa Times that it was so disappointing to note that MANEB has allocated supervisors and invigilators some of whom are commuting for a distance of 20 to 40 Kilometres with unrealistic allowances a distance that should have been accorded residential status “MANEB has of late been registering success in the administration of national examinations This is because they have been hiring teachers with integrity and these teachers have been sacrificing At the centre of each national examination administration there is a teacher who is a supervisor or invigilator “MANEB should not choose to punish a teacher MANEB should realise that every quality work goes with costs and there is no short cut to realising quality work,” charged Moyo MANEB received the letter from SESTU but has not yet responded until when this chaos has come along Moyo added that said SESTU does not want the forthcoming Malawi School Certificate of Education (MSCE) Examinations to be disrupted because of this current mess “MANEB has time to sort out this mess before the worst comes to the worst,” he said The Malawi School Certificate of Education (MSCE) Examinations will run from 2nd July to 26th July 2024 while the Junior Certificate of Education (JCE) Examinations currently under way will end on 13th June After several months of failed negotiations with the government healthcare workers have finally resolved to hold nation-wide sit in beginning.. Metrics details Organic–inorganic perovskites are a class of solution-processed semiconductors holding promise for the realization of low-cost efficient solar cells and on-chip lasers Despite the recent attention they have attracted fundamental aspects of the photophysics underlying device operation still remain elusive Here we use photoluminescence and transmission spectroscopy to show that photoexcitations give rise to a conducting plasma of unbound but Coulomb-correlated electron–hole pairs at all excitations of interest for light-energy conversion and stimulated optical amplification The conductive nature of the photoexcited plasma has crucial consequences for perovskite-based devices: in solar cells it ensures efficient charge separation and ambipolar transport while it provides a low threshold for light amplification and justifies a favourable outlook for the demonstration of an electrically driven laser whose cross-section for carrier capture is however low yielding a minor impact on device performance partly organic and partly inorganic compound it is not clear in principle whether the excited-state dynamics will be dominated by excitonic effects These experimental results indicate that the injected electron–hole gas thermalizes at the conduction and valence band extremes to form an ionized electron–hole plasma and a negligible exciton population even for excitation regimes for which thermodynamic considerations would predict a transition to an insulating excitonic gas Such photophysics resembles the excited-state properties of model inorganic semiconductors with direct bandgap energy and small exciton binding energies We were also able to investigate the influence of trap states which are expected to be plentiful in a solution-processed traps have a low capture cross-section and play a minor role both for photovoltaic energy conversion and light amplification (a) Visible–near-infrared absorption (continuous line) and luminescence (dashed line) spectra of a MAPbI3 film (thickness Spontaneous emission was excited by a green laser (λ=532 nm) operating in continuous wave (cw) (b,c) Continuous lines: theoretical fits to the experimental absorption spectra at 170 and 300 K Excitonic and band-to-band oscillator strengths are calculated taking into account Coulomb interaction according to Elliott’s theory of Wannier excitons Short-dashed (long-dashed) lines: band-to-band contributions with (without) the inclusion of Coulomb interactions The PL spectrum consists of a single line slightly shifted to the red with respect to the excitonic absorption peak. As shown in Supplementary Fig. 3 the energy shift is mostly caused by self-absorption due to the finite thickness of the film The shape of the emission corrected for self-absorption and the emission in thinner films is almost coincident with the excitonic resonance while the shape is slightly asymmetric towards the higher energy side These results point to the intrinsic nature of the emitting species The emission narrows and blueshifts with decreasing temperature following the shift in the absorption spectrum We modelled the absorption coefficient α(ħω) near the band edge in the framework of the Elliot’s theory of Wannier excitons36: The comparison between experiment and theory shows the crucial role of electron–hole correlation effects in optical transitions near the band edge The absorption coefficient of correlated electron–hole pairs is over a factor of two larger than that one calculated for uncorrelated free carriers in a wide spectral window above the bandgap Time-integrated photoluminescence signals (TIPL) for the two perovskite samples (MAPbI3 red dots MAPbI3−xClx blue dots) are plotted on the left axis as a function of the injected carrier density the laser pulse fluence directly measured in the experiments is also reported on the top axis The dashed lines correspond to the prediction from a rate equation model accounting for the main relaxation channels for electrons and holes Simulations take into account the exponential spatial profile of the electron–hole density created by laser pulses The initial dependence on the injected carrier density is superlinear The injected carrier density is calculated multiplying the laser pulse photon fluence by the absorption coefficient of the films The emission quantum yields (QY) are calculated as TIPL/Φ Initially the QY grows with fluence for both films as the bimolecular recombination becomes faster and a growing fraction of the injected excitations recombine radiatively The absolute QY is scaled to match theoretical predictions The maximum QY values are ~30% for MAPbI3 and >70% for MAPbI3−xClx The dotted lines represent predictions from the same-rate equation model employed for the TIPL The very good agreement between model and data indicates that the main photophysical processes are accounted for in the model we investigate the electron–hole recombination by studying the dependence on the pulse fluence of (i) the temporal-integrated PL intensity (TIPL); (ii) the PL quantum yield QY and (iii) the initial PL decay rate Figure 3 shows the TIPL intensity and the relative QY for the same films investigated in Fig. 2 The TIPL grows quadratically until n0~1017 cm−3 before showing some saturation at higher fluences This nonlinear behaviour can be ascribed to the interplay between density-dependent radiative and non-radiative recombination mechanisms We rationalize the recombination kinetics as follows: for n0<1017 cm−3 carrier trapping is faster than radiative recombination; the increase of the QY with pulse fluence is then associated with the increase of the bimolecular radiative recombination rate When this latter becomes faster than trapping (n0>1017 cm−3) If the injected electron–hole population is further increased density-dependent non-radiative processes become more and more important and eventually dominate The decay rates for the transient photoluminescence signal decays are plotted as a function of the injected carrier density (or laser pulse fluence on top axis). The rates, defined as are extracted from the data in Fig. 2a,b Such rates represent therefore the very initial decay and should not be mistaken for the average photoluminescence decay rate obtained by fitting the entire decay with an exponential function from a least square fit to an exponential decay and are reported only when they exceed the size of the marker the rates are very similar for the two perovskites (although the average exponential decay rates are significantly different) and grow together for growing injected carrier densities We infer that such rates measure the intrinsic density-dependent bimolecular and Auger recombination processes The dotted lines represent the outcome of the rate equation model: also in this case the agreement with the experiment is satisfactory Experimental and theoretical decay rates represent an exponential fit to the initial photoluminescence transients carried out in the same time-window for experiments and simulations The exponential spatial profile of the electron–hole density created by laser pulses is accounted for in the model simulations After analyzing the initial decay rates, we then proceeded to simulate the time integral of PL, namely TIPL and the QY as a function of the pulse fluence (reported in Fig. 3) We solved the rate (equations (2) and (3)) for the carrier population and the PL in which we included (i) the radiative recombination rate taken from equation (2) (ii) the electron–hole annihilation rate via non-radiative Auger processes proportional to γn3 and (iii) a monomolecular decay ktn to describe carrier trapping the red line represents the hole density nh the dotted line is the density of filled traps nt As the excitation intensity grows the traps are filled until the density of electrons and holes is large enough that the bimolecular recombination becomes faster than the trapping rate therefore stopping the accumulation of electrons in the traps c shows a sketch of the relaxation of optical excitations under steady-state conditions (VB and CB mark the valence and conduction bands required for optical amplification is achieved for I~15 kW cm−2 with an increase by a factor of 3 with respect to the case in which Auger recombination is switched off The radiative recombination rate of the plasma population is found to be in agreement with the rate of spontaneous emission predicted by the Kubo–Martin–Schwinger law providing a bimolecular decay constant kb=2.6 × 10−10 cm3 s−1 the population dynamics is governed by the competition of two nonlinear processes the radiative bimolecular recombination rate and Auger carrier annihilation (Auger constant The maximum PL quantum yield is achieved for density range n0=0.5–3 × 1018 cm−3 We show that Auger processes do not preclude sustaining a plasma population of n~2 × 1018 cm−3 under cw excitation; yet they increase the required laser intensity from I~5 kW cm−2 to I~15 kW cm−2 the latter corresponding to a current density of 5.5 kA cm−2 for electrical injection of the plasma A legitimate question is what happens to the correlated electron–hole plasma in the high-carrier density regime where amplified stimulated emission and lasing have been observed Is light amplification provided by an electron–hole plasma or by a bound-exciton gas energy conservation imposes that the extra energy of the recombining electron–hole pair is redistributed among the remaining carriers A quantum-mechanical analysis thus provides a possible explanation for the intriguing experimental observations of a PL peaked at EX but scaling quadratically with the excitation power we conclude that the presence of the electron–hole plasma justifies a low-density threshold radiative bimolecular decay dominates over carrier trapping by defect states and non-radiative Auger decay the latter prevailing at higher electron–hole densities All these features make organometal perovskites very promising for the realization of a solution-processed electrically driven laser The CH3NH3I salt was crystallized at 50 °C using a rotary evaporator until the powder reached a white-brown colour The salt was then washed and filtered three times with diethyl ether and dried in vacuum overnight to finally obtain a white powder All the reactants were purchased from Sigma-Aldrich Perovskite solutions of MAPbI3 and MaPbI3−xClx were obtained by dissolving MAI and PbI2 or PbCl2 in a 1:1 or 3:1 molar ratio in anhydrous dimethyl sulphide in air at room temperature The solutions were stirred for 12 h before film deposition Films were obtained by spinning the solution on top of soda lime glass substrates at 1,000 r.p.m for 120 s at room temperature inside a nitrogen-filled glove box Before deposition the substrates were cleaned with water and soap rinsed with acetone and ethanol and dried with dry air The as-deposited films were thermally treated at 100 °C for 1 h on a hot plate inside the glove box to obtain the perovskite structure crystallization The light yellow fresh films turned brown after a few minutes of treatment thus confirming the crystal formation but it was necessary to increase the treatment time up to 1 h to achieve the structure stability Structural characterization was carried out by analyzing the X-ray diffraction patterns recorded by a Bruker D8-Discover diffractometer for thin films with parallel beam geometry and Cu Kα wavelength Symmetric ω-2θ scans were obtained using a step size of 0.02° and time per step of 4 s Film thickness and surface morphology were obtained by atomic force microscopy (AFM) with a NT-MDT Solver P47H-Pro in semicontact mode by a high-resolution non-contact silicon tip Optical absorption was measured with films kept in vacuum inside a cold finger cryostat and illuminated by an incandescent tungsten lamp through parabolic mirror optics An optical chopper was used to modulate the light intensity in time The transmitted light was dispersed with a grating spectrometer (Acton 2300 series with a 50 g mm−1 600 nm blaze grating) and detected by a diode and a lock-in amplifier tuned to the optical chopper frequency The temperature was varied using liquid nitrogen as a coolant samples were excited with a Nd:Yag cw laser (Spectra Physics Millennia series) and the optical emission collected with a grating spectrometer (Acton 2500 series 500 nm blaze) coupled to a liquid nitrogen cooled CCD camera (Princeton Instruments) Samples were kept in vacuum and the optical emission was dispersed by a spectrometer (Acton 2300 series with a 50 g mm−1 600 nm blaze grating) coupled to a streak camera (Hamamatsu C5640) The optical resolution depended on the time range employed on the streak camera and therefore varied from few tens of picoseconds to over 300 ps Samples under vacuum were excited with a 527 nm Nd:Ylf laser either in pulsed mode (1.1 KHz repetition rate 600 nm blaze grating) and detected by a diode Correlated electron–hole plasma in organometal perovskites Organometal halide perovskites as 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optical absorption by excitons Semiconducting tin and lead iodide perovskites with organic cations: phase transitions and near-infrared photoluminescent properties Optical absorption of gallium arsenide between 0.6 and 2.75 eV New analysis of direct exciton transitions: application to GaP The Photophysics behind Photovoltaics and Photonics WILEY-VCH Verlag GmbH&Co Density dependence of the electron-hole plasma lifetime in semiconductor quantum wells Statistical-mechanical theory of irreversible processes general theory and simple applications to magnetic and conduction problems Electronic theory of the optical properties of laser-excited semiconductors Energy transfer in nanostructured oligothiophene inclusion compounds Ultrafast formation of nonemissive species via intermolecular interaction in single crystals of conjugated molecules Three-dimensional energy transport in highly luminescent host-guest crystals: a quantitative experimental and theoretical study Competition between band gap and yellow luminescence in GaN and its relevance for optoelectronic devices Excitonic trions in undoped GaAs quantum wells Direct observation of the Mott transition in an optically excited semiconductor quantum well Many-body dynamics and exciton formation studied by time-resolved photoluminescence Determination of the exciton formation in quantum wells from time-resolved interband luminescence Excitonic photoluminescence in semiconductor quantum wells: plasma versus excitons Light-induced charged and trap states in colloidal nanocrystals detected by variable pulse rate photoluminescence spectroscopy Colloidal Bi2S3 nanocrystals: quantum size effects and midgap states Download references Filippetti for useful discussions regarding the electronic properties of organometal perovkites This work has been funded by Regione Autonoma della Sardegna through PO-FSE Sardegna 2007–2013 gratefully acknowledges financial support by Regione Autonoma della Sardegna Project n° 15 ‘New materials for photovoltaics solar energy conversion’ Operational Programme of the Autonomous Region of Sardinia European Social Fund 2007–2013—Axis IV Human Resources Objective l.3 and Line of Activity l.3.1 ‘Avviso di chiamata per il finanziamento di Assegni di Ricerca.’ Dipartimento di Scienze Chimiche e Geologiche Data analysis and simulations were done by M.S XRD and AFM measurements were done by D.M. All Authors contributed to the discussion and the preparation of the manuscript The authors declare no competing financial interests Supplementary Methods and Supplementary References (PDF 1003 kb) Reprints and permissions Download citation Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science Metrics details Solution-based methods represent the most widespread approach used to deposit hybrid organic-inorganic perovskite films for low-cost but efficient solar cells solution-process techniques offer limited control over film morphology and crystallinity and most importantly do not allow sequential film deposition to produce perovskite-perovskite heterostructures Here the successful deposition of CH3NH3PbI3 (MAPI) thin films by RF-magnetron sputtering is reported an industry-tested method to grow large area devices with precisely controlled stoichiometry MAPI films are grown starting from a single-target made of CH3NH3I (MAI) and PbI2 with a barely detectable content of unreacted PbI2 full surface coverage and thickness ranging from less than 200 nm to more than 3 μm Light absorption and emission properties of the deposited films are comparable to as-grown solution-processed MAPI films The development of vapor-phase deposition methods is of interest to advance perovskite photovoltaic devices with the possibility of fabricating perovskite multijunction solar cells or multicolor bright light-emitting devices in the whole visible spectrum even optimized solution-process methods are affected by shortcomings One is a lack of control over the low-temperature crystallization process which is affected by many factors such as solvents and precursors solvent evaporation during the deposition and annealing conditions often leading to poor reproducibility of films morphology properties that in turn have crucial influences on the photovoltaic performance is that sequential film deposition from solution cannot produce perovskite-perovskite heterostructures since the solvent employed in depositing subsequent layers washes away the underlying ones multijunction tandem solar cells and p-n junctions all perovskite based are advancing very slowly these methods are expected to provide purity of precursors and deposited films due to the vacuum environment and fine control of the deposition parameters resulting in a high level of perovskite crystallization and reproducible films vapor methods are suited for a scale-up preparation and large area deposition It is crucial that vapor methods do not require the use of solvents and of annealing steps allowing perovskite-on-perovskite deposition to create heterostructures and junctions We propose here a route based on a sputtering technique to provide highly reproducible single-phase hybrid perovskite films with the added bonus of being an industry-tested technique for large area film growth The relatively lower deposition efficiency of sputtering is overcome by a magnetron-based device no reports about the deposition of hybrid perovskites thin films by sputtering has been reported Motivated by the above reported issues related to the preparation of hybrid organic-inorganic perovskites films in this paper we demonstrate the successful one-pot growth of methylammonium lead iodide CH3NH3PbI3 (MAPI) films by means of RF-magnetron sputtering starting from a single target made of a CH3NH3I (MAI) and PbI2 mixture with a 30% w/w excess of MAI Sputtering technique allows to finely tune the deposition conditions by adjusting different parameters such as and target to substrate distance thus providing an excellent platform to further optimize perovskite films as well as to extend the approach presented here for MAPI to any other material of interest in the field of Perovskite Solar Cells (PSCs) Figure 1A presents a sketch of the MAPI thin films growth method used in the present work, i.e. the RF-magnetron sputtering starting from a target made of MAI and PbI2 with a MAI excess of 30 wt%. Depositions were carried out at a RF-power of 40 W, with argon (P = 2   × 10−2 mbar) as the sputtering gas in the DC-bias mode by setting its value to 80 V. (A) Schematic representation of the sputtering deposition method used in the present work to growth MAPI thin films; (B) XRD patterns of MAPI films reported in Table 1 Figure 1B shows the x-ray diffraction patterns (XRD) of a series of representative MAPI films with variable thicknesses from below 200 nm (Film 1) up to about 3.2 μm (Film 9) (details are reported in Table 1) Optimal growth conditions were obtained after extensive optimization work and are reported in the Experimental Section The starting target for the sputtering deposition was a mixture of MAI and PbI2 with a 30% w/w excess of MAI it can be observed a slight preferential growth along the (00 l) directions as suggested by the relative intensity of the experimental peaks corresponding to the (002) and (004) reflections compared to the calculated intensities No significant shifts of the peaks as a function of film thickness are evident in the XRD patterns The surface morphology of the MAPI films has been investigated by Atomic Force Microscopy (AFM). Figure 2 reports some selected images of films with variable thickness. AFM topography images of MAPI film over 40 × 40 μm for film 1 (A) SEM images of MAPI film 4 (A) magnification at 20 kX and (B) magnification at 100 kX) and film 7 (C) magnification at 20 kX and (D) magnification at 100 kX) Photoluminescence and absorptance spectra of MAPI films Blue line: absorptance (A) spectrum of the film No The black and red lines are the photoluminescence spectra The former is the directly measured spontaneous emission spectrum The second one is the emission spectrum calculated from the absorptance by using the reciprocity relation; the sharp drop of the calculated emission intensity at the low energy side of the spectrum stems from the experimental noise of the absorptance baseline Directly measured photoluminescence spectra of various films Photoluminescence dependence on excitation light intensity Log-log plot of the photoluminescence intensity versus laser intensity The photoluminescence signal follows a power law as a function of the laser intensity the power index is m = 1; at higher excitation densities Insets: recombination processes at low and high intensities Electrons and holes mostly decay non-radiatively via mid-gap energy traps (dashed line) which are assumed to capture only one type of carrier the majority of holes are generated by ionization of shallow acceptors (unintentional chemical doping) the majority of holes are generated by light a high concentration of free holes in the valence band (VB) is created which turns out as a sort of photodoping because most of electrons are trapped and the subsequent concentration of free electrons in the conduction band (CB) remains low Decay curves of the spectral-integrated photoluminescence signal for four films of different thicknesses Photoluminescence spectrograms of film 5 and 7 Spectra of the spontaneous emission emitted in time window delimited by the red and green rectangles shown in the spectrograms reported in the central panels We reported the successful deposition of MAPI thin films by RF-magnetron sputtering MAPI films were grown starting from a single-target made of MAI and PbI2 (with a 30% w/w excess of MAI) and appeared to be single-phase with full surface coverage and thickness ranging from less than 200 nm to more than 3 μm The optical properties of the deposited films are comparable to as-grown solution-processed MAPI films and the photoluminescence quantum yield could be substantially improved with post-growth passivation treatments The development of vapor-phase deposition methods is of great interest in the current research on hybrid perovskites in view of a scale-up of device fabrication the precise control of stoichiometry and the possibility of growing perovskite-perovskite heterostructures Thin films of MAPI have been deposited on amorphous silica substrates (MaTek 1 nm) by means of radio frequency magnetron sputtering starting from a MAI/PbI2 mixture (Aldrich thickness 1 cm) was made of pressed powders of MAI/PbI2 mixture Depositions parameters were: i) target-to-substrate distance The depositions have been carried out in DC-bias mode by setting the value to 80 V (with respect to the target electrode) thus assuring a good control over the deposition rate Film thickness has been determined by means of a mechanical profilometer The structural properties of the deposited thin films were characterized by X-ray diffraction (XRD) by means of a Bruker D8 Advance instrument (Cu radiation) in a Bragg-Brentano set-up Reflectance (R) and transmittance (T) measurements were performed at 8° angle of incidence using a dual-beam spectrophotometer with an integrating sphere accessory (Agilent Cary 5000 UV-Vis-NIR) Samples were mounted excited by a regenerative amplifier laser (Coherent Libra) delivering 100-fs-long pulses at a repetition rate of 1 KHz Photoluminescence was dispersed with a grating spectrometer (Princeton Instruments Acton SpectraPro 2300i equipped with a 50 gr/mm grating blazed at 600 nm) dispersed and detected by a streak camera (Hamamatsu) Samples were excited by a diode-pumped Nd:YVO4 CW laser at 532 nm (Spectra Physics Millennia) Photoluminescence was dispersed by a grating spectrometer (Princeton Instruments Acton SpectraPro 2300i) and detected by a LN-cooled CCD camera (Princeton Instruments PIXIS) laser beam was chopped to reduce the overall thermal loading Surface topography and film roughness were measured by atomic force microscopy (AFM) with a NT-MDT Solver P47H-Pro instrument in semi contact mode at 1 Hz scan speed by a Etalon high-resolution non-contact silicon tip Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites II Solvent engineering for high-performance inorganic-organic hybrid perovskite solar cells Structure and Growth Control of Organic–Inorganic Halide Perovskites for Optoelectronics: From Polycrystalline Films to SingleCrystals A fast deposition-crystallization procedure for highly efficient lead iodide perovskite thin-film solar cells Efficient planar heterojunction perovskite solar cells by vapour deposition Organometal halide perovskite thin films and solar cells by vapor deposition Research Update: Hybrid organic-inorganic perovskite (HOIP) thin films and solar cells by vapor phase reaction APL Scalable fabrication of perovskite solar cells Vapor-Deposited Perovskites: The Route to High-Performance Solar Cell Production Photovoltaic Devices Employing Vacuum-deposited Perovskite Layers Tuning the Light Emission Properties by Band Gap Engineering in Hybrid Lead Halide Perovskite Physics of solar cells: from basic principles to advanced concepts Optical determination of Shockley-Read-Hall and interface recombination currents in hybrid perovskites Band filling with free charge carriers in organometal halide perovskites Can Trihalide Lead Perovskites Support Continuous Wave Lasing Origin and elimination of photocurrent hysteresis by fullerene passivation in CH3NH3PbI3 planar heterojunction solar cells Giant switchable photovoltaic effect in organometal trihalide perovskite devices Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions and Near-Infrared Photoluminescent Properties Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber Long-range balanced electron- and hole-transport lengths in organic-inorganic CH3NH3PbI3 Why Lead Methylammonium Tri-Iodide Perovskite-Based Solar Cells Require a Mesoporous Electron Transporting Scaffold (but Not Necessarily a Hole Conductor) Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of SingleCrystals Controllable Growth of Perovskite Films by Room‐Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells Surface Charge Trapping in Organolead Halide Perovskites Explored by Single-Particle Photoluminescence Imaging Optical characterizations of the surface states in hybrid lead–halide perovskites Influence of growth temperature on bulk and surface defects in hybrid lead halide perovskite films Impact of microstructure on local carrier lifetime in perovskite solar cells Download references The authors gratefully acknowledge the project PERSEO-“PERovskite-based Solar cells: towards high Efficiency and lOng-term stability” (Bando PRIN 2015-Italian Ministry of University and Scientific Research (MIUR) Decreto Direttoriale 4 novembre 2015 n performed the AFM and absorbance measurements analyzed the optical measurements and wrote part of the paper; M.P contribute with experimental design and L.M coordinated the work and wrote part of paper related to film growth and structural characterization The authors declare no competing interests Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41598-018-33760-w Journal of the European Optical Society-Rapid Publications (2021) Journal of Coatings Technology and Research (2021) thought she was from a small town until she came to Cathlamet Metrics details Metal-halide perovskite solar cells rival the best inorganic solar cells in power conversion efficiency In order for the technology to mature and approach the ideal Shockley-Queissier efficiency experimental tools are needed to diagnose what processes limit performances beyond simply measuring electrical characteristics often affected by parasitic effects and difficult to interpret Here we study the microscopic origin of recombination currents causing photoconversion losses with an all-optical technique measuring the electron-hole free energy as a function of the exciting light intensity Our method allows assessing the ideality factor and breaks down the electron-hole recombination current into bulk defect and interface contributions providing an estimate of the limit photoconversion efficiency without any real charge current flowing through the device We identify Shockley-Read-Hall recombination as the main decay process in insulated perovskite layers and quantify the additional performance degradation due to interface recombination in heterojunctions equilibrium conditions of the solar cell in the dark impose that the concentration of trapped electrons varies across the intrinsic layer: trap levels at the centre of the i-semiconductor traps are half-filled so that the recombination rate RSRH,e(h) of the excess carriers is quite large trap levels close to the ETL (HTL) are filled (empty) no trapping of electrons (holes) by mid-gap states is thereby possible Here we propose an optical experimental method to estimate the voltage drop caused by each type of nonradiative channel we studied the free energy of the electron-hole pairs (μ) as a function of the intensity of the exciting light (Iex) We then show how to get information on the ideality factor and recombination channels the optical approach can be used to study the double heterojunctions composing the solar cells as well as the two single heterojunctions and the absorbing layer alone thereby providing a comparative method to discriminate between interface and bulk recombination JPL can be opportunely expressed in terms of the external photoluminescence quantum yield (EQYPL) defined as the ratio between JPL and the absorbed excitation photon flux equation (1) can be reformulated to explicitly link μ to EQYPL: the free energy is provided by the difference between the energies of the quasi-Fermi levels of electrons in the ETL and in the HTL at the opposite side of the device in the intrinsic layer equates the circuit voltage V of the solar cell if Fcb and Fvb do not vary from the transport materials up to the external contacts where represents the mean carrier generation rate per unit of volume the electron (hole) extraction rate per unit of volume and α denotes the number of carriers involved in the recombination process (α = 1,2,3 for monomolecular and trimolecular recombinations respectively) To connect μ to the free electron (ne) and hole (nh) concentrations generalized to account for non-equilibrium carriers: where ni is the free-carrier concentration of the intrinsic semiconductor in the dark Grey markers represent the measured free energy μoc as a function of the excitation intensity (Iex) delivered by a CW laser at 532 nm The orange box encloses the dispersion of μoc for samples fabricated with a variety of different techniques μoc depends linearly on ln(Iex) with a slope m of approximately 3/2 regardless of the fabrication method yielding an average ideality factor (within one standard deviation) Shockley-Read-Hall recombinations are expected to lead to a rational ideality factor m = 3/2 at low illumination levels The experimental slope decreases to approximately 2/3 for Iex > 100 W/cm2 the rate of photons absorbed by the film matches that one obtained at an illumination level of one sun (AM 1.5G) with a free energy loss due to Shockley-Read-Hall recombinations The free energy μoc was estimated through eq (2) by simply adding to the radiative limit μoc,rad the term kTln(EQYPL) due to nonradiative recombinations Experimental data show that μ is proportional to ln(Iex) with the slope coefficient giving the ideality factor independently of the method used to fabricate the MAPbI3 films just swapping the roles of electrons and holes The capture rate of electrons by intragap levels can be described as a bimolecular process where nh,t is the density of trapped holes in the intrinsic semiconductor all traps are nearly empty so nh,t is almost equal to the density Nt of recombination centres the recombination process is monomolecular (αe = 1) but in this case the densities of both trapped electrons ne,t and free holes nh increase with the excitation intensity and Hole recombination is therefore an effective bimolecular process with αh = 2; far from trap saturation We thus conclude that nonradiative recombinations in HPs can be described in the framework of the SRH model SRH recombination limits the available free energy to eV with a loss at one sun excitation  =  eV; lower losses could be achieved by reducing the trap density We rule out trap saturation because it would cause hole recombination to become monomolecular as the population of trapped electrons becomes constant and consequently m should increase from 3/2 to 2 (αe = αh = 1) According to the optical reciprocity relation in eq a purely optical analysis of the EQYPL ought to establish if additional interface recombination is setting stricter limits to μoc in single and double HP heterojunctions with respect to the bulk (a) Top axis: experimental free energy μoc under 50 mW/cm2 CW laser excitation at 532 nm Bottom axis: external photoluminescence quantum yield (EQYPL) under the same conditions The rate of photons absorbed by the film matches that of an illumination level of one sun (AM 1.5G) Two types of single heterojunctions are reported: i-ETL (where the ETL is compact TiO2) and HTL-i (where the HTL is spiro-MeOTAD) Heterojunctions introduce non-radiative recombination channels resulting in a lower free energy with respect to the single perovskite layer (b) Schematic representation of electron-hole recombination processes in a heterojunction: bulk Shockley-Read-Hall decays (cyan arrow) radiative decays (black arrow) and interface decays (orange arrow); the sketch refers to the ETL side interface Markers represent the measured free energy μoc of electron-hole pairs in perovskite and perovskite-based heterojunctions as a function of the excitation intensity (Iex) delivered by a CW laser at 532 nm Lines are provided as a guide to the eye to identify the slope of the data The ideality factor deviates from the 1.5 value of the single hybrid perovskite layer increasing to 2 when Iex exceeds a threshold that is peculiar to each type of heterojunction Interface decay processes are not elementary decays and the ideality factor is expected to increase with the excitation intensity Excitation-dependent band bending and modification of the energy level alignment close to the junctions could drive non-linear phenomena for the carrier dynamics at the two interfaces the fact that at one sun m ≈ 2 suggests monomolecular recombinations for both electrons and holes (αe ≈ αh ≈ 1) Full circles stand for Je(h)(μ) estimated from the measured diode current Jrec(μoc) with the substitution μoc → μ The dotted lines mark the point of maximum extraction of electrical power Red curves and circles: electron (hole) current density in the double heterojunction; recombination is dominated by interface electron and hole annihilations Cyan curves and circles: electron (hole) current density in the single hybrid perovskite layer; recombination is due to electron and hole Shockley-Read-Hall annihilations alone Dashed line: Je(h)(μ) in the Shockley-Queissier limit The Shockley-Queissier model provides the reference ultimate limit performance of single junction photovoltaic devices assuming only radiative recombinations and neglecting all losses due to charge transport and extraction We have developed an all-optical experimental method to assess the deterioration of photoconversion performances with respect to the Shockley-Queissier limit due to nonradiative recombinations the proposed approach allows measuring the upper limit to the open-circuit voltage of a solar cell set by nonradiative electron-hole decays in the intrinsic materials and assessing to what extent each interface in the device introduces additional recombination currents We are able to identify the nature of decay processes showing that recombinations in single perovskite layers can be described by the Shockley-Read-Hall model in the presence of defects that preferentially trap either electrons or holes We estimate the ideality factor and the limit of the solar cell efficiency without any current flowing through the device non-ideal contacts and charge transport losses Aldrich) were mixed at 0 °C and stirred for 2 h The precipitate was recovered byevaporation at 50 °C for 1 h The product was washed with diethyl ether three times and finally dried at 60 °C in a vacuum oven for 24 h Glass substrates (Visiontech) and FTO-coated glass substrates (Solaronix) were cleaned by ultrasonication in a deionized water Substrates were treated to the TL1-washing procedure (washed in double distilled water (Milli-Q water) hydrogen-peroxide (H2O2) and ammonia (NH3) 5:1:1 v/v at 80 °C for 10 minutes) then rinsed in double distilled water prior next depositions A 80 nm-thick TiO2 dense hole-blocking layer (ETL) was deposited on glass/FTO by spin coating a commercial titaniumdiisopropoxidebis(acetylacetonate) solution (75% in 2-propanol Sigma-Aldrich) diluted in butanol (0,15 M) twice at 3,000 rpm for 60 sec and annealed at 125 °C As last step a 0.3 M solution is spin-coated The prepared CH3NH3I and commercial PbI2 (99.99% ultradry Alfa Aesar) were stirred in a mixture of γ-butyrolactone (GBL) and DMSO (2:1vol/vol; GBL The perovskite precursor solution was coated onto either glass or TiO2/FTO substrate by a consecutive two-step spin-coating process at 1,000 and 4,000 r.p.m for 10 and 60 s respectively with a dripping of dichloromethane at 10 s to the end the films were annealed on a hotplate at 100 °C for 10 min either a PMMA solution (80 mg/1 mL chloroform) or the spiro-MeOTAD solution was spin-coated on the perovskite layer at 2,500 r.p.m A spiro-MeOTAD solution was prepared by dissolving 90 mg of spiro-MeOTAD in 1 ml chlorobenzene (99.8% to which were added 28.8 μl of 4-tert-butylpyridine (96% 17.5 μl lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) solution (520 mg LI-TSFI in 1 ml acetonitrile This fabrication process was carried out under controlled atmospheric conditions with a humidity of <1% and a temperature between 20 and 25 °C we determined a perovksite film thickness of 160 nm FTO-coated glass substrates (Solaronix) were cleaned by ultrasonication in deionized water A 80 nm-thick TiO2 dense hole-blocking layer (bl-TiO2) was then deposited on the substrates by spin coating at 3,000 rpm for 60 sec and annealed at 520 °C using a commercial titanium diisopropoxide bis(acetylacetonate) solution (75% in 2-propanol The prepared CH3NH3I and commercial PbI2 (99% Alpha Aesar) for the 1 M CH3NH3PbI3 solution were stirred in a mixture of γ-butyrolactone (GBL) and DMSO (2:1 vol/vol; GBL these precursor solutions were filtrated using a hydrophilic PTFE syringe filter (pore size of 22 μm) The filtrated perovskite precursor solution was coated onto bl-TiO2/FTO substrate by a consecutive two-step spin-coating process at 1,000 and 4,000 r.p.m for 10 and 60 s respectively with a dipping of dicloromethan at 10 sec to the end the spiro-MeOTAD solution was spin-coated on the perovskite layer at 2,500 r.p.m 17.5 μl lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) solution (520 mg LI-TSFI in 1 ml acetonitrile 80 nm gold was thermally evaporated on top of the device at a pressure of 5 × 10−6 mbar for 30 min to form the back contact The active area of the complete device was 0.09 cm−2 The irradiance of the beam was calculated as Eexc = P/A The samples were placed into an integrating sphere (Newport 819C-IS-5.3) and both the scattered laser light and the photoluminescence light were collected through a fibre-optic cable (Avantes FC-V200-1-SR) coupled to a grating spectrometer (Princeton Instruments Acton SpectraPro 2500i equipped with a 150 gr/mm 600 nm blaze grating) and detected by a LN-cooled CCD camera The laser beam was angled so that its reflection and/or the PL emission did not strike the output port directly The spectral response of the detection system has been calibrated so that the number of counts is proportional to the number of photons collected (a) Le is the spectrally integrated intensity of the laser striking the inside of the empty integrating sphere; (b) L0 is the spectrally integrated intensity of the laser striking the inside of the integrating sphere with the sample inside the sphere but not under direct excitation; (c) E0 is the spectrally integrated intensity of the photoluminescence from the sample under indirect excitation; (d) Li is the spectrally integrated intensity of the laser directly illuminating the sample; (e) Ei is the spectrally integrated intensity of the photoluminescence as a result of direct excitation the measurements were not corrected for self-absorption Samples were placed in a vacuum chamber and excited with a diode-pumped Nd:YVO4 CW laser (Millennia V) at 532 nm The photoluminescence was dispersed with a grating spectrometer (Princeton Instruments Acton SpectraPro 2500i equipped with a 150 gr/mm A New Silicon p-n Junction Photocell for Converting Solar Radiation into Electrical Power Best Research-Cell Efficiencies. NREL. nrel.gov Available at: http://www.nrel.gov/pv/assets/images/efficiency_chart.jpg (Accessed: 27 October 2016) (2016) High-efficiency two-dimensional Ruddlesden– Popper perovskite solar cells High-performance photovoltaic perovskite layers fabricated through intramolecular exchange Perovskite Solar Cells: From Materials to Devices Advancements in perovskite solar cells: photophysics behind the photovoltaics Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance Improving efficiency and stability of perovskite solar cells with photocurable fluoropolymers Quantum dot–induced phase stabilization of α-CsPbI3 perovskite for high-efficiency photovoltaics Detailed Balance Limit of Efficiency of p‐n Junction Solar Cells A mixed-cation lead mixed-halide perovskite absorber for tandem solar cells Perovskite-perovskite tandem photovoltaics with optimized band gaps Observation of a hot-phonon bottleneck in lead-iodide perovskites Role of microstructure in the electron–hole interaction of hybrid lead halide perovskites Excited State Properties of Hybrid Perovskites Photovoltaic materials: Present efficiencies and future challenges Towards stable and commercially available perovskite solar cells Defects in perovskite-halides and their effects in solar cells The Theory of p-n Junctions in Semiconductors and p-n Junction Transistors Radiative efficiency of state-of-the-art photovoltaic cells Radiative efficiency of lead iodide based perovskite solar cells Predicting the open-circuit voltage of CH3NH3PbI3 perovskite solar cells using electroluminescence and photovoltaic quantum efficiency spectra: The role of radiative and non-radiative recombination On the Uniqueness of Ideality Factor and Voltage Exponent of Perovskite-Based Solar Cells Hole-conductor-free perovskite organic lead iodide heterojunction thin-film solar cells: High efficiency and junction property Statistics of the Recombinations of Holes and Electrons Trap‐Assisted Non‐Radiative Recombination in Organic–Inorganic Perovskite Solar Cells Efficient luminescent solar cells based on tailored mixed-cation perovskites Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency Characterization of Planar Lead Halide Perovskite Solar Cells by Impedance Spectroscopy and Intensity-Modulated Photovoltage/Photocurrent Spectroscopy Quantification of spatial inhomogeneity in perovskite solar cells by hyperspectral luminescence imaging Reciprocity relation between photovoltaic quantum efficiency and electroluminescent emission of solar cells Methylammonium fragmentation in amines as source of localized trap levels and the healing role of Cl in hybrid lead-iodide perovskites High Charge Carrier Mobilities and Lifetimes in Organolead Trihalide Perovskites Interface engineering of highly efficient perovskite solar cells Highly efficient planar perovskite solar cells through band alignment engineering Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic Ch3NH3PbI3 An Improved Experimental Determination of External Photoluminescence Quantum Efficiency Download references Cardini and the INFN (National Institute for Nuclear Physics) for lending us the integrating sphere for the quantum yield measurements and by MIUR (Italian Ministry of University and Research) through Progetto di ricerca PON R&C 2007–2013 (Avviso n del 29 ottobre 2010) MAAT-Molecular NAnotechnology for HeAlth and EnvironmenT (Project Number: PON02_00563_3316357) and PRIN PERrovskite-based Solar cells: towards high Efficiency and lOng-term stability (PERSEO) European Social Fund 2007–2013 - Axis IV Human Resources Objective l.3 and Line of Activity l.3.1 ‘Avviso di chiamata per ilfinanziamento di Assegni di Ricerca.’ We acknowledge Progetto di ricerca PON R&C 2007–2013 (Avviso n del 29 ottobre 2010) MAAT-Molecular NAnotechnology for HeAlth and EnvironmenT (Project Number: PON02_00563_3316357) acknowledges Regione Puglia and ARTI for funding FIR - future in research projects “PeroFlex” project no Polo di Nanotecnologia c/o Campus Ecotekne prepared and characterized the materials; V.S Download citation Teachers in public secondary schools in Malawi have finally launched their own union to advance their interests effectively renouncing their membership from from their long-time mother body Christened Secondary School Teachers Union (SESTU) the union envisages to work with education stakeholders in creating conducive working and learning environment to promote and maintain high quality education standards SESTU interim president Pilirani Kapolo justified the establishment of a separate union targeting secondary school teachers in public schools saying apart from being their constitutional right to form or join a trade union of their choice they felt TUM was becoming overstretched to fully represent teachers’ needs as the number of teachers in public schools kept increasing “Experience has shown that TUM acts swiftly on issues related to teachers from public primary schools than issues related to teachers from public secondary schools This leaves secondary school teacher with inadequate representation Issues related to primary schools are handled by the Directorate of Basic Education in the Ministry of Education issues for secondary schools are handled by the Directorate of Secondary Education,” said Kapolo He said currently Education Division Managers (EDMs) are the ones who manage secondary school teachers while District Education Managers (DEMs) are handling primary school teachers Kapolo further stated that the creation of the new union has been necessitated by increasing unprofessional conduct of secondary school teachers which affects delivery of quality secondary education “SESTU would be there to compliment government efforts on the same We want to promote inclusive education in secondary in sub-sector with motivated special need teachers,” he emphasized SESTU interim General Secretary (GS) Druwen Frank Moyo said their union is now the legal mouthpiece for secondary school teachers in public schools in Malawi Moyo brushed away speculations that the Tonse Alliance government has facilitated the formation of the union to destabilize TUM which has recently given the government headache over risk allowances TUM has announced that it will be mobilizing the teachers to go on strike again accusing the government of not living up to its word on risk allowances By calling yourselves ‘Legal mouth piece’ of Secondary school Teacher’s how would you treat those who won’t be part of ‘assembly’ Malimba cadetized TUM with his stupid demands Sports journalists in the country have been asked to include minor sporting disciplines in their schedules as they cover sports... Teachers across the country have expressed dismay over video clips sponsored by the Teachers Council of Malawi (TCM) arguing they are an insult and demeaning to the teaching career The video clips which are making rounds in the social media often have one or two drunken characters who are present at the duty station and fail to clearly understand the role of the Teachers Council of Malawi The teachers argue that the clips are portraying teachers in the country as dull and excessive beer drinkers who are unnecessarily resisting the recent establishment of TCM in the country “What do they want to achieve by discussing issues of teachers through drunken characters in such video clips?” wondered one teacher who did not want to be named “This is sheer demeaning of our career as if it’s a profession of drunkards They should have found a better way of convincing teachers to register with them,” echoed another General Secretary for the Teachers Union of Malawi (TUM) said it was sad to see such a portrayal of teachers in the social media “I don’t think the Teachers Council can sponsor people to be insulting teachers in those video clips Something is missing and it might not be the aim of the council for those actors to be using such kind of sarcasm Such productions are coming from their own heads and TCM should tame those actors because teachers are furious with such portrayal,” remarked Kumchenga Secondary School Teachers Union (SESTU) General Secretary said teachers were not comfortable with the picture that the video clips were painting We are aware that TCM is on a sensitisation campaign using several avenues including that of use of video clips circulating in the social media we are not comfortable with the picture some of the video clips are portraying “It is our plea to TCM that as they embark on the sensitisation campaign it would be unfair to use tools or weaponry that in the end goes against the very teachers they are targeting They should use avenues that respect the teacher out there,” Moyo said But one of the producers and actors of the video clips in circulation argues that what they are doing is just acting and there is no intention to demean the teachers Said Kamwendo: “we are not trying to portray teachers as drunkards People should understand that this is just acting and that person takes that character of a drunkard in many of our sketches “The paramount reason for featuring that character is to advocate against such behaviours Remember that with the introduction of these TCM licences one’s licence will be withdrawn by government if there is evidence of such malpractices.” The Teachers Council of Malawi was established in 2022 by an Act of Parliament and is set to regulate the teaching profession in Malawi ensuring high standards and professionalism among educators received letters of credence from four non - resident diplomatic envoys - An kashe mutane 2 tare da raunata wasu uku a sabon rikicin da ya barke da yammacin jiya a karamar hukumar Barkin Ladi da ke jihar Filato - Rahotanni sun bayyana cewar an kashe mutanen biyu ne yayin da su ke dawowa daga gona - An kai harin ne a yankin Nding Sestu mai makwabtaka da kasuwar 'yan dankali a karamar hukumar Jos ta kudu Mutane biyu aka kashe tare da raunata wasu uku a sabon rikicin da ya barke da yammacin jiya Rahotanni sun bayyana cewar an kashe mutanen biyu ne yayin da su ke dawowa daga gona Kazalika an bayyana cewar wadanda su ka kawo harin sun tsere da wata motar daukan kaya da ke cike da kayan miya wani mai sana'ar sayar da kayan miya da na gini a kasuwar karamar hukumar Jos ta kudu ya bayyana cewar dukkan mutanen da aka kashe mazauna garin Barkin Ladi ne Umar ya kara da cewar an binne mutanen biyu safiyar yau Duk da bai samu damar amsa kiran da aka yi masa ba kakakin rundunar 'yan sanda a jihar Filato ya tabbatar wa da jaridar Premium Times batun kisan mutanen ta hanyar takaitaccen sakon waya DUBA WANNAN: Machina: Gari a arewa da macizai ke kaiwa Sarki gaisuwa kwamandan rundunar soji ta Ofireshon safe haven "An kai harin ne a yankin Nding Sestu mai makwabtaka da kasuwar 'yan dankali "Jam'ian mu sun gaggauta zuwa wurin amma bayan isar sun samu mutane biyar da aka harba amma daga baya an tabbatar da mutuwar biyu daga cikinsu bayan an kai su babban asibitin garin Barkin Ladi," a cewar Umar Umar ya kara da cewar dakarun soji na aiki domin ganin an kama wadanda su ka kai harin Muhimmiyar sanarwa: Shafin NAIJ.com Hausa ya koma LEGIT.ng Hausa Latsa wannan domin samun sabuwar manhajar labarai ta Legit.ng Hausa a wayar ku ta hannu: https://play.google.com/store/apps/details?id=ng.legit.hausa&hl=en Ku biyo mu a shafukanmu na dandalin sada zumunta: Facebook: https://facebook.com/legitnghausa Idan kuna da wata shawara ko bukatar bamu labari