Search

Solution-processed photodetectors could be of use in large-area light-sensing applications because they can be fabricated at low cost on plastic substrates and their absorption spectra can be tuned by chemical design. However, fabricating photodetectors with low dark currents and integrating them into high-resolution backplanes remains challenging. Here we show that solution-processed metal halide perovskite photodiodes on top of an amorphous indium gallium zinc oxide transistor backplane can be used to create a flexible image sensor that is ~100 μm thick and has a resolution of 508 pixels per inch. We have developed a pixel edge cover layer for the system that reduces electrode current leakage and thus dark current density. The low noise current in combination with high external quantum efficiency results in high photodetectivity at wavelengths from 550 nm to 770 nm. We show that our imager can be used for document scanning and biometric fingerprinting and that it can be wrapped around objects with radii as small as 0.6 cm. Low-dark-current perovskite photodetectors can be integrated with an oxide transistor backplane to create a high-resolution optical scanning array capable of imaging flat and curved surfaces.

Ten years after the first paper(1) on the properties of metal halide perovskite solar cells, their efficiency and stability have increased tremendously.(2) It was quickly realized that their application goes beyond the single-junction use. Indeed, perovskite cell technology, by virtue of its tunable bandgap and low sub-bandgap absorption, offers new opportunities for stacking solar cells of different bandgap in a multijunction device to overcome the fundamental Shockley–Queisser (SQ) efficiency limit of a single-junction device. Under AM1.5 irradiation, this limit is 33.7% for the optimal bandgap, and for perovskite with a normally somewhat higher bandgap of 1.55 eV it drops to 31%.(3,4) It is not expected that perovskite will exceed 26% single-junction efficiency.(5) For crystalline silicon solar cells (c-Si), including Auger recombination, the theoretical SQ limit is 29.4%.(6,7) Currently, single-junction silicon solar cells reached an efficiency in the lab of 26.7%;(8,9) while in mass production, solar cells are produced with efficiencies up to about 25%,(10) with main stream efficiencies of about 22%. The latter have been increasing by 0.4%/year, and this trend is expected to continue for a number of years, but it will likely become overly costly to go beyond 24–25%. This efficiency increase has contributed significantly to the steep learning rate, which is the average reduction of Si PV module selling price for every doubling of cumulative shipment, of 39.8%(11) that has been experienced since 2006. Although the manufacturing cost reduction also plays a major role, we expect that when the practical efficiency limits are being approached, the silicon PV industry will not be able anymore to maintain such a learning rate. Aside from module price, the further PV system costs (like installation) to a large extent depend on area and are reduced per unit of power output simply by higher module efficiency. It is because of the possibility that it can help overcome both these performance and cost limitations that metal halide perovskite-on-silicon tandem devices have been under development since 2015(12) and today lead to power conversion efficiencies of over 29%.(13,14)

In recent years, organometal halide perovskite based photovoltaics have attracted great interest for their high power conversion efficiency (PCE) potentially at low manufacturing cost. Despite the massive progress made by the community, the long-term performance stability and the manufacturability at large scale remain very challenging. In this work, we demonstrate a stable and scalable architecture for perovskite module fabrication. Thermal evaporation assisted 2-step approach is employed for the 1.53 eV perovskite deposition. For high throughput processing, NiOx by linear reactive sputtering is developed as the inorganic hole transport layer (HTL). PCE of 20% is achieved for the solar cell. Perovskite modules with monolithic series interconnected cells by picosecond laser scribing based on the developed cell stack are also fabricated. Above 80% of the initial efficiency is retained after 1000 hrs of thermal mono-stress at 85°C in N2 atmosphere.

Sputtered transparent conducting oxides (TCOs) are widely accepted transparent electrodes for several types of high-efficiency solar cells. However, the different sputtering yield of atoms makes stoichiometric transfer of target material challenging for multi-compounds. Additionally, the high kinetic energies of the arriving species may damage sensitive functional layers beneath. Conversely, pulsed laser deposition (PLD) is operated at higher deposition pressures promoting thermalization of particles. This leads to stoichiometric transfer and additionally reduces the kinetic energy of ablated species. Despite these advantages, PLD is rarely used within the photovoltaic community due to concerns about low deposition rates and the scalability of the technique. In this study, wafer-scale (4-inch) PLD of high-mobility Zr-doped In2O3 (IZrO) TCO for solar cells is demonstrated. IZrO films are grown at room temperature with deposition rate on par with RF-sputtering (>4 nm min−1). As-deposited IZrO films are mostly amorphous and exhibit excellent optoelectronic properties after solid phase crystallization at

Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis.

Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis., This article is based upon work from COST Action StableNextSol MP1307 supported by COST (European Cooperation in Science and Technology). M.V.K., E.A.K., V.B. and A.O. thank the financial support of the United States – Israel Binational Science Foundation (grant no. 2015757). E.A.K., A.A. and I.V.-F. acknowledge partial support from the SNaPSHoTs project in the framework of the German-Israeli bilateral R&D cooperation in the field of applied nanotechnology. M.S.L. thanks the financial support of National Science Foundation (ECCS, award #1610833). S.C., M.Manceau and M.Matheron thank the financial support of European Union’s Horizon 2020 research and innovation programme under grant agreement no 763989 (APOLO project). F.D.R. and T.M.W. would like to acknowledge the support from the Engineering and Physical Sciences Research Council (EPSRC) through the SPECIFIC Innovation and Knowledge Centre (EP/N020863/1) and express their gratitude to the Welsh Government for their support of the Ser Solar programme. P.A.T. acknowledges financial support from the Russian Science Foundation (project No. 19-73-30020). J.K. acknowledges the support by the Solar Photovoltaic Academic Research Consortium II (SPARC II) project, gratefully funded by WEFO. M.K.N. acknowledges financial support from Innosuisse project 25590.1 PFNM-NM, Solaronix, Aubonne, Switzerland. C.-Q.M. would like to acknowledge The Bureau of International Cooperation of Chinese Academy of Sciences for the support of ISOS11 and the Ministry of Science and Technology of China for the financial support (no. 2016YFA0200700). N.G.P. acknowledges financial support from the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science, ICT Future Planning (MSIP) of Korea under contracts NRF-2012M3A6A7054861 and NRF-2014M3A6A7060583 (Global Frontier R&D Program on Center for Multiscale Energy System). CSIRO’s contribution to this work was conducted with funding support from the Australian Renewable Energy Agency (ARENA) through its Advancing Renewables Program. A.F.N gratefully acknowledges support from FAPESP (Grant 2017/11986-5) and Shell and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation. Y.-L.L. and Q.B. acknowledge support from the National Science Foundation Division of Civil, Mechanical and Manufacturing Innovation under award no. 1824674. S.D.S. acknowledges the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (HYPERION, grant agreement no. 756962), and the Royal Society and Tata Group (UF150033). The work at the National Renewable Energy Laboratory was supported by the US Department of Energy (DOE) under contract DE-AC36-08GO28308 with Alliance for Sustainable Energy LLC, the manager and operator of the National Renewable Energy Laboratory. The authors (J.J.B, J.M.L., M.O.R, K.Z.) acknowledge support from the ‘De-risking halide perovskite solar cells’ program of the National Center for Photovoltaics, funded by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technology Office. The views expressed in the article do not necessarily represent the views of the DOE or the US Government. H.J.S. acknowledges the support of EPSRC UK, Engineering and Physical Sciences Research Council. V.T. and M.Madsen acknowledge ‘Villum Foundation’ for funding of the project CompliantPV, under project no. 13365. M.Madsen acknowledges Danmarks Frie Forskningsfond, DFF FTP for funding of the project React-PV, no. 8022-00389B. M.G. and S.M.Z. thank the King Abdulaziz City for Science and technology (KACST) for financial support. S.V. acknowledges TKI-UE/Ministry of Economic Affairs for financial support of the TKI-UE toeslag project POP-ART (no. 1621103). RC thanks the grants for Development of New Faculty Staff, Ratchadaphiseksomphot Endowment Fund. A.D.C. gratefully acknowledges funding from the European Union’s Horizon 2020 Research and Innovation Program (grant agreement no. 785219-GrapheneCore2 and no. 764047-ESPResSo). M.L.C. and H.X. acknowledges the support from Spanish MINECO for the grant GraPErOs (ENE2016-79282-C5-2-R), the OrgEnergy Excellence Network CTQ2016-81911- REDT, the Agència de Gestiód’Ajuts Universitaris i de Recerca (AGAUR) for the support to the consolidated Catalonia research group 2017 SGR 329 and the Xarxa de Referència en Materials Avançats per a l’Energia (Xarmae). ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya.

In this work, we present an extensive characterization of plasma-assisted atomic-layer-deposited SnO2 layers, with the aim of identifying key material properties of SnO2 to serve as an efficient electron transport layer in perovskite solar cells (PSCs). Electrically resistive SnO2 films are fabricated at 50 °C, while a SnO2 film with a low electrical resistivity of 1.8 × 10-3 ω cm, a carrier density of 9.6 × 1019 cm-3, and a high mobility of 36.0 cm2/V s is deposited at 200 °C. Ultraviolet photoelectron spectroscopy indicates a conduction band offset of ∼0.69 eV at the 50 °C SnO2/Cs0.05(MA0.17FA0.83)0.95Pb(I2.7Br0.3) interface. In contrast, a negligible conduction band offset is found between the 200 °C SnO2 and the perovskite. Surprisingly, comparable initial power conversion efficiencies (PCEs) of 17.5 and 17.8% are demonstrated for the champion cells using 15 nm thick SnO2 deposited at 50 and 200 °C, respectively. The latter gains in fill factor but loses in open-circuit voltage. Markedly, PSCs using the 200 °C compact SnO2 retain their initial performance at the maximum power point over 16 h under continuous one-sun illumination in inert atmosphere. Instead, the cell with the 50 °C SnO2 shows a decrease in PCE of approximately 50%. © 2018 American Chemical Society.

Scalable sheet-to-sheet slot die coating processes have been demonstrated for perovskite solar cells and modules. The processes have been developed on 6 in. × 6 in. glass/ITO substrates for two functional layers: the perovskite photo-active layer and the Spiro-OMeTAD hole transport layer. Perovskite solar cells produced using these slot die coating processes demonstrate device performances identical to the spin coated devices. All manufactured devices illustrate a high level of reproducibility. The developed slot die coating processes were also used for the manufacturing of perovskite PV modules. Large area modules of 12.5 × 13.5 cm2 were realized by slot die coating on 6 in. × 6 in. substrates in combination with newly developed laser ablation processes for conventional P1-P2-P3 monolithic cell interconnections. The modules demonstrate power conversion efficiencies above 10%, with a power output of 1.7 W. This achievement is an important milestone in the development of up-scalable manufacturing technologies for perovskite PV modules.

A two-step sequential deposition method has been applied to prepare the solar cells with two types of perovskites Cs0.15FA0.85Pb(I0.95Cl0.05)3 and Cs0.15FA0.85Pb(I0.95Br0.05)3. In order to obtain the perovskite layers, the different sources of bromine and chlorine atoms were used for synthesis. The performance and time stability of chloride-based photocells are worse in comparison to the bromide-based devices. It can be explained by the effect of an accumulation of Cl atoms at the interfaces between the chloride-based perovskites and the layer of PCBM. Such a process causes an increasing of interface recombination. Also, the bulk density of states and, consequently, the bulk recombination of charge carriers seem to be higher for the perovskite layers obtained with chlorine atoms. The two-step technique applied to create the bromide perovskites less influences the photocells performance as in the case of one-step deposition. We can explain this observation by an existence of nucleation sites in the inorganic layer which improve the growth of a perovskite material.

In order to commercialize the perovskite solar cells (PSC) technology, efficient and industrial deposition methods over large areas have to be adopted, and the device architectures have to provide long term stability. In this work we combine several upscalable deposition methods to develop a stable semitransparent PSC. The control of the uniformity of perovskite crystallization by tailoring the ink formulation and the drying process was pursued in order to drastically reduce the efficiency losses over an area increase of 3 orders of magnitude (from 0.04 to 100 cm2). When adopting sputtered ITO as top electrode, the stack retains up to 90% of the initial performance after 1000hrs at 85 °C. The use of laser patterning to define P1 P2 and P3 scribes for series interconnected modules enables the fabrication of thermally stable minimodule (4cm2) and large module (100cm2). Finally an outlook on the use of the perovskite device as top cell in a 4T tandem architecture with commercial c-Si cells will be provided.

In order to achieve the highest performance of organometal trihalide perovskite solar cells, it is required to recognize the dominant mechanisms which play a key role in a perovskite material. In the following studies, we have focused on the interfacial recombination between the hole transporting layer (HTL) and the perovskite CH3NH3PbI3 in solar cell devices with p–i–n architecture. It has been shown that Cu:NiOx used as HTL drastically decreases a short–circuit photocurrent (Jsc) and an open–circuit voltage (Voc). However, we have found that an addition of PTAA thin layer improves cells quality and, as a consequence, the efficiency of such solar cells increases by 2%. Here, we explain both Jsc and Voc losses with a theory of the “dead layer” of perovskite material where a very high surface recombination occurs. We demonstrate the numerical and experimental studies by the means of series detailed analyses to get in–depth understanding of the physical processes behind it. Using a drift–diffusion model, it is shown that the presence of a parasitic recombination layer influences mostly the current distribution in the simulated samples explaining Jsc and Voc losses. The following results could be useful for improving the quality of perovskite solar cells.

This article presents an innovative and low-cost solution for optimizing the acquisition of performance data of small-laboratory-scale photovoltaic devices. A novel measuring setup is proposed, designed based on an Arduino microcontroller and low-cost components, coupled with open source hardware and software. The manuscript describes in detail the instrument design, components and assembly enabling the reproduction and customization of the instrument for any reader. The setup is combined with an optional web-platform, which enables fast analysis and comparison of the collected data. For the demonstration of the instrument in operation, comparison of measurements of solar cell with the developed setup and commercial products has been conducted. It is shown that the presented prototype provides values of accuracy and precision during I-V curve recording, comparable with the values measured using a commercial source-meter (Keithley 2400). The study also discusses the unique advantages of easy transport and data collection by the setup and the drawbacks in the hardware, which have been observed during a round robin study. © 2019 IOP Publishing Ltd.

We report a cooperative study conducted between different laboratories to investigate organic solar cell degradation with respect to P3HT material properties and different solar cell architectures. Various batches of P3HT were collected from different suppliers reflecting commercial availability as well as properties variability. Among the materials properties explicitly considered were the molar mass, dispersity, regio-regularity, impurities by trace metals and intrinsic doping evaluated from radical concentrations. Each of the participating laboratories contributing test devices applied their own layer stack, i.e. their own device architecture and layout. This variation was appreciated as another parameter for evaluation. Even though a large amount of devices failed due to extrinsic degradation effects, indeed, some materials properties were found to be more important than others for obtaining long lifetimes and high stability of P3HT-based polymer solar cells., All authors are grateful for support from COST Action MP 1307, “StableNextSol”. This article is based upon work from COST Action StableNextSol project MP1307, supported by COST (European Cooperation in Science and Technology). RM, TF, DF, RR and HH are grateful for financial support within the frame of “AIMS in OPV” junior research group by the BMBF, Germany. L.C. is thankful to ENEA (Ente Nazionale Energia e Ambiente) and the Italian Ministry of Foreign Affairs for a visitor post-doc fellowship to BGU. FG and MD are grateful for financial support by the National Center for Research and Development within the Project POSCIS under Grant No. LIDER/09/129/L-3/11/NCBR/2012). IVF and EAK acknowlegde financial support from Adelis Foudation. N. Blaubach is acknowledged for ICP measurements. MP thanks the Bundesministerium für Bildung und Forschung, Germany (BMBF FKZ 03EK3507).

In this work, efficient rigid and flexible semi-transparent perovskite solar cells (ST-PSCs) were prepared in inverted (light incidence through hole transport layer) configuration. All layers were deposited by a combination of low-temperature solution-based, sputtering and spatial atomic layer deposition (sALD) techniques, which can be potentially up-scalable for sheet to sheet and roll to roll manufacturing lines. The rigid and flexible opaque PSCs reach stabilized power conversion efficiency (PCE) of 19% and 16% [1], while rigid ST-PSC reaches 16.4% stabilized PCE. Besides those results, we have developed our current flexible opaque stack to the flexible semi-transparent stack using top TCO electrode and sALD buffer layer. We also highlight that the inverted configuration exhibited extremely high infrared transparency [2] and a remarkable stability during the light and thermal stress. The encapsulated ST-PSCs retained 93% of their initial stabilized PCE after 3000h aging at 85°C in a nitrogen atmosphere. Interestingly, using highly transparent transport layers, rigid and flexible ST-PSCs show comparable efficiency by illumination from both rear and front TCO sides, resulting in a bifacility of 99%.

The chemistry of the interface between the metal halide perovskite absorber and the charge transport layer affects the performance and stability of metal halide perovskite solar cells (PSCs). The literature provides several examples of poor PSC conversion efficiency values, when electron transport layers (ETLs), such as SnO2 and TiO2, are processed by atomic layer deposition (ALD) directly on the perovskite absorber. In the present work, we shed light on the chemical modifications occurring at the perovskite surface, during ALD processing of SnO2 and TiO2, in parallel with the evaluation of the PSC cell performance. The ALD processes are carried out on a (Cs,FA)Pb(I,Br)3 perovskite by adopting tetrakis(dimethylamino)tin(IV) and tetrakis(dimethylamino)titanium(IV) as metal precursors and H2O as the coreactant for SnO2 and TiO2, respectively. Perovskite surface modification occurs in the form of an ultrathin PbBr2 layer. Furthermore, in the case of SnO2, halogen molecules are detected at the interface, in parallel with the initial growth of an oxygen-deficient SnO2. Subgap defect states just above the valence band maximum of SnO2 are also detected. These states act as hole traps at the perovskite/SnO2 interface, subsequently promoting charge recombination and deteriorating the performance of the cell. We hypothesize that a redox reaction between the perovskite, or its decomposition products, and the Sn metal center of the ALD precursor takes place: I− and Br− are oxidized to I2 and Br2, respectively, and Sn(IV) is reduced to Sn(II). In contrast, the Ti(IV) metal center does not undergo any redox process, and, as a result, a promising 11% power conversion efficiency is measured with TiO2 as the ETL. This result strongly suggests that TiO2 may be a more suitable ETL, when processed directly on the perovskite absorber.

In this contribution the development of highefficiency planar semi-transparent perovskite solar cells (STPSCs) for tandem applications is presented. The ST-PSC absorber layer, and electron and hole transport layers were processed using spin coating. The near-infrared (NIR) transmission of the ST-PSC is optimized by improving ITO material quality and tuning the thickness of component layers in cells for optimal light management, leading to a high NIR transmittance of about 93%. In combination with a SunPower IBC cell of 23.8% single-junction efficiency, a 4-terminal (4T) perovskite/c-Si tandem cell efficiency of 26.1% is achieved. In combination with a metal-wrap-through n-PERT c-Si cell laminate of 18.6% efficiency, a 4T perovskite/c-Si tandem cell efficiency of 24.1% is demonstrated, showing that a very significant efficiency gain can be obtained on lower performance c-Si cells.

The replacement of the conventional top metal contact with a semi-transparent conducting electrode such as sputtered indium-tin oxide (ITO) is strictly required to adopt the perovskite solar cell (PSC) in hybrid tandem photovoltaic applications. In order to prevent sputtering damages on the perovskite absorber and the organic materials adopted in p-i-n planar architecture, an atmospheric pressure spatial atomic layer deposited (s-ALD) ZnO buffer layer has been included. The use of a 45 nm thick s-ALD layer enables the fabrication of a PSC with a power conversion efficiency (PCE) of 14.7%, with a similar PCE when illuminated from the ITO/s-ALD ZnO side. When adopted in a four terminal configuration with a c-Si solar cell (PCE of 18.6%), a 2.5% absolute PCE gain is observed with respect to the stand alone c-Si. Finally, the semi-transparent PSC shows an excellent shelf life, and only −4% degradation on the tracked maximum power point when encapsulated and aged at 65 °C in an inert atmosphere after 1500 h.

In this work, we present an extensive characterization of plasma-assisted atomic-layer-deposited SnO

The industrialization of perovskite solar cells (PSC) require processes to efficiently deposit the constituent layers over large areas. In this work we optimized the use of slot die coating process for both sheet-to-sheet (S2S) and roll-to-roll (R2R) manufacturing. Particular focus have been put on the control of the uniformity of perovskite crystallization by tailoring the ink formulation and the drying process in order to avoid any efficiency losses over an area increase of 3 orders of magnitude (from 0.09 to 144 cm2). In this way we were able to fabricate 144 cm2 modules with 13.8% stabilized efficiency on aperture area on glass (14.5% on active area). At the same time, by developing the R2R slot die deposition process of the perovskite layer, we demonstrated 160 cm2 flexible module with 10.1 % stabilized efficiency on aperture area (11.0% on active area). In addition, fully R2R coated cells exhibit up to 16% efficiency. An outlook on how to upscale more stable perovskite cells (i.e. with pin structure) will be given. These results prove how to optimize the upscaling process towards large area manufacturing of perovskite solar modules on both rigid and flexible substrate.

Perovskite solar cells (PSCs) are emerging among the photovoltaic (PV) technologies due to their high power conversion efficiency (PCE) in combination with potentially low cost manufacturing processing. In this contribution, the fabrication of efficient planar n-i-p PSCs by the modification of the electron transport layer (ETL) adopted as n-type contact is demonstrated. Specifically, a fluorine-based plasma treatment prior to perovskite deposition leads to surface fluorination of the TiO2 ETL. The presence of fluorine on the TiO2 surface drastically improves the adhesion between the ALD layer and the methylammonium lead iodide perovskite film, and leads to a more favourable energy band alignment, accompanied by a faster electron carrier extraction at the interface. As consequence of surface fluorination, we observe a significant reduction in the current density-voltage curve hysteresis with respect to the ALD based reference sample, as well as a remarkable improvement in power conversion efficiency from 4% up to a stable 14.8%.

In order to bring the organo-lead halide perovskite solar cells (PSC) towards the commercialization, the device stability needs to be drastically improved. Our approach relies on the introduction of a compact metal oxide (MeO) layer in a p-i-n planar architecture by means of atmospheric pressure spatial atomic layer deposition (s-ALD) technique. The presence of this additional layer improves the stability towards the ambient environment as well as during a thermal stress test carried out at 85°C. Furthermore, we observe that replacing the top metal contact with a sputtered ITO electrode can prolong the device stability both under thermal and light soaking tests. © 2018 IEEE.

The perovskite/c-Si tandem technology is considered as a cost-effective approach to realize a cell efficiency beyond the limit of single-junction (SJ) c-Si cells. Compared to its counterpart of 2-terminal (2T) configuration, 4-terminal (4T) tandem has the advantages such as no constraint of current matching and potentially simple mechanical stacking. But one of the largest challenges is the limited near-infrared (NIR) transmission of the semi-transparent perovskite solar cell (ST-PSC), which has been a bottleneck to the c-Si bottom cell performance and eventually the whole tandem cell performance. The highest NIR transmittance that has been reported is about 84%. In this contribution, we demonstrate a p-i-n planar ST-PSC with an efficiency as high as 15.7% and with a record NIR transmittance of about 92%. It is realized by optimization of the tin-doped indium oxide (ITO) material properties and light management. This NIR-transparent and high-efficiency ST-PSC leads to a 4T tandem cell efficiency of 25.7%, using an interdigitated-back-contact (IBC) c-Si bottom cell. © 2018 Elsevier B.V.

In this study, the fabrication of highly efficient and durable flexible inverted perovskite solar cells (PSCs) is reported. Presynthesized, solution-derived NiOx and ZnO nanoparticles films are employed at room temperature as a hole transport layer (HTL) and electron transport layer (ETL), respectively. The triple cation perovskite films are produced in a single step and for the sake of comparison, ultrasmooth and pinhole-free absorbing layers are also fabricated using MAPbI3 perovskite. The triple cation perovskite cells exhibit champion power conversion efficiencies (PCEs) of 18.6% with high stabilized power conversion efficiency of 17.7% on rigid glass/indium tin oxide (ITO) substrates (comparing with 16.6% PCE with 16.1% stabilized output efficiency for the flexible polyethylene naphthalate (PEN)/thin film barrier/ITO substrates). More interestingly, the durability of flexible PSC under simulation of operative condition is proved. Over 85% of the maximum stabilized output efficiency is retained after 1000 h aging employing a thin MAPbI3 perovskite (over 90% after 500 h with a thick triple cation perovskite). This result is comparable to a similar state of the art rigid PSC and represents a breakthrough in the stability of flexible PSC using ETLs and HTLs compatible with roll to roll production speed, thanks to their room temperature processing.

Stabilities of ITO-containing and ITO-free organic solar cells were investigated under simulated AM 1.5G illumination and under concentrated natural sunlight. In both cases ITO-free devices exhibit high stability, while devices containing ITO show degradation of their photovoltaic performance. The accelerated degradation under concentrated sunlight (of up to 20 suns) in ITO-containing devices was found to be reversible. Dark exposure of degraded samples can partly restore performance. A possible underlying mechanism for such a phenomenon is discussed.

Organometallic halide perovskite solar cells (PSCs) are extremely promising novel materials for thin-film photovoltaics, exhibiting efficiencies over 22% on glass and over 17% on foil 1, 2. First, a sheet-to-sheet (S2S) production of PSCs and modules on 152x152 mm2 substrates was established, using a combination of sputtering, e-beam evaporation, slot die coating and thermal evaporation (average PCE of 14.6 ± 1.3 % over 64 devices, more than 10% initial PCE on modules). Later the steps towards a roll-to-roll production will be investigated, starting from the optimization of the stack to make it compatible with a faster production at low temperature. A water based SnOx nanoparticles dispersion was used as solution processable ETL, and the deposition process was scaled-up from spin coating to R2R slot die coating on a 300 mm wide roll of PET/ITO. R2R production is often carried out in ambient atmosphere and involve the use of large volumes of materials, thus a first point is the development of a green solvent and precursor system for the perovskite layer to prevent the emission of toxic compound in the environment. The first results on device fabrication are encouraging, which allow partial R2R manufacturing of flexible PSC (R2R coating of SnOx and perovskite, S2S for Spiro-OMeTAD and gold) with stabilized PCE of 12.6%, a remarkable value for these novel devices. This result can be considered an important milestone towards the production of efficient, low cost, lightweight, flexible PSC on large area.

Solar cells are generally optimised for operation under AM1.5 100 mW cm(-2) conditions. This is also typically done for polymer solar cells. However, one of the entry markets for this emerging technology is portable electronics. For this market, the spectral shape and intensity of typical illumination conditions deviate considerably from the standard test conditions (AM1.5, 100 mW cm(-2), at 25 degrees C). The performance of polymer solar cells is strongly dependent on the intensity and spectral shape of the light source. For this reason the cells should be optimised for the specific application. Here a theoretical model is presented that describes the light intensity dependence of P3HT:[C60] PCBM solar cells. It is based on the Shockley diode equation, combined with a metal-insulator-metal model. In this way the observed light intensity dependence of P3HT:[C60] PCBM solar cells can be described using a 1-diode model, allowing fast optimization of polymer solar cells and module design.

Organic and hybrid perovskite based solar cells have a huge potential to significantly contribute to a clean electricity supply of the future. However, so far they exhibit complex and hierarchical degradation paths and their understanding can only be acquired through the application of complementary chemical and physical characterization techniques. This limited device stability is the main hurdle for a successful and large scale market introduction of these emerging solar cell technologies. Our StableNextSol Action has created a highly interdisciplinary network of laboratories, as well as corresponding industry, overall more than 120 partners, with complementary analytical techniques for the study and understanding of the degradation mechanisms occurring in state-of-the-art devices. Our Action integrates and generates fundamental knowledge and expertise to foster disruptive innovations targeted to mitigate device failure and to propose and develop new concepts for more stable solar cells. Value is added to the entire value chain of photovoltaic research at European and international level, as well as variety decision makers in the public sector by supporting specialisation policy and standards still lacking in this research field. The outcome of the Action will contribute to resolve the global challenges facing the industry and this COST Action initiative has brought together all these expertises and resources to promote the cooperation between different sectors, academia, public authorities and industry.

Solution processing of OPVs on industrial scale brings some challenges, such as finding alternative, non-chlorinated solvents and using roll-to-roll compatible processes. Here we present a fully inkjet printed tandem OPV device, which consists of up to 9 sequentially inkjet printed layers. The inkjet printed layers are made without chlorinated solvents using an industrial scale printhead, making the processing industrial viable.The main challenge for inkjet printing this tandem structure was to find a good way to print the recombination contact consisting of a closed PEDOT:PSS layer from a water based solution onto a hydrophobic P3HT:PCBM layer and on top of that a ZnO layer. Previously it was shown by our group that ZnO can be inkjet printed on a PEDOT:PSS layer, however, when modifying (commercial) PEDOT:PSS formulations the resulting surface energy of this PEDOT:PSS layer changes and hence the printability of ZnO on top of the PEDOT:PSS is different. Careful optimization of the full recombination contact was done and tandem devices were successfully inkjet printed.The voltage of the inkjet printed tandem we present here is the sum of the voltages of the subcells, which shows that there are no voltage losses over the recombination contact. The efficiency of the inkjet printed tandems was higher than the efficiencies of the respective single junction devices. These results show that inkjet printing is a promising technique to up-scale the production of tandem OPVs and commercialization is one step closer.

Polymer solar cells offer a promising low cost alternative in photovoltaics if the expensive ITO electrode can be omitted. Recently an alternative based on highly conductive PEDOT:PSS in combination with current collecting grids was developed.1 Electrical modeling is carried out to optimize the grid pattern in these polymer solar cells. The basic inputs for this type of modeling are the resistivity of the materials, film thicknesses and the diode parameters of the solar cell. The diode parameters are often determined by fitting the experimental current-voltage measurements to a one-diode model. This gives the well-known dark saturation current density (J0), diode ideality factor (n), photocurrent density (JL), shunt resistance and series resistance. However, the fitted parameters do not always correspond with the intrinsic solar cell parameters, i.e. those that correspond to an infinitesimally small diode, but they are actually lumped parameters containing information of the heterogeneity of the system. For this reason, two one-diode fits corresponding to two different systems (in size and geometry) can yield different intrinsic diode parameters. The reason for this can be found in the heterogeneity of the system. We show an approach to determine the so-called intrinsic diode parameters, by fitting the experimental IV curve against a simulated IV curve that is obtained from a model in which the experimental solar cells are explicitly modeled in 3D. This model provides a simple basis to determine the intrinsic solar cell parameters that can be used for the optimization of grid patterns for polymer solar cells.

A new encapsulation method for organic solar cells has been tested on flexible solar modules and cells embedded in polyurethane, sandwiched between a tempered glass plate and a polycarbonate plate. Panels, each containing 10 organic solar modules/cells, were fabricated and installed for outdoor exposure in eight different countries for 4½ months. In order to minimize potential deviations in procedures and equipment, one person was responsible for the fabrication, installation and initial and final IV-measurements of the panels using the same equipment for all measurements and calibrations. The encapsulated modules/cells showed significantly reduced degradation compared with previous studies, with final average efficiencies around 40% of the original after 4½ months outdoor exposure. Photodegradation was furthermore found not to be the primary source of degradation., This work was supported by: The Danish Strategic Research Council (DSF2104-07-0022) and EUDP (64009-0050and64011-0002). The European Commission as part of the Framework 7 ICT 2009 collaborative project HIFLEX (Grant agreement no.248678), the Dutch Polymer Institute (DPI Project no.678) and by Agentschap NL within the project OZOFAB (grant no. EOSLT1002). AM and EAK a financial support from the European Commission’s Seventh Framework Program (FP7/2007-2013) under Grant Agreementno.261936. The UK Big Lottery Fund/OPAL project for the London pyronometer data.

Indium-tin-oxide (ITO) free polymer solar cells prepared by ink jet printing a composite front electrode comprising silver grid lines and a semitransparent PEDOT:PSS conductor are demonstrated. The effect of grid line density is explored for a large series of devices and a careful modeling study enabling the identification of the most rational grid structure is presented. Both optical and light beam induced current (LBIC) mapping of the devices are used to support the power loss model and to follow the evolution of the performance over time. Current generation is found to be evenly distributed over the active area initially progressing to a larger graduation in areas with different performance. Over time coating defects also become much more apparent in the LBIC images.

The presence of a transparent conductive electrode such as indium tin oxide (ITO) limits the reliability and cost price of organic photovoltaic devices as it is brittle and expensive. Moreover, the relative high sheet resistance of an ITO electrode on flexible substrates limits the maximum width of a single cell. We have developed an alternative ITO-free transparent anode, based on solution processed high conductive PEDOT:PSS in combination with a printed current collecting grid. The screen printed silver grid demonstrates a typical sheet resistance of 1 Ω/□ with 6.48% surface coverage. The efficiency of a flexible device with an active area of 4 cm\2 with such a grid is much higher than a similar device based on ITO. Furthermore, as this composite anode is solution-processed, it is a step forward towards low-cost large area processing. © 2010 Elsevier B.V. All rights reserved.

In order to reach the objective of low-cost, large area organic photovoltaic systems, we build up a knowledge base concerning the influence of process conditions on the performance of polymer solar cells. A large area solar cell module, with roll-to-roll coated PEDOT:PSS and photoactive layers (based on P3HT:[C60]PCBM blend) on a flexible substrate, has been demonstrated. Both the PEDOT:PSS and photoactive layer were deposited by slot die coating. A non-chlorinated solvent was used for the deposition of the photoactive blend. The flexible solar cell module illustrated a power conversion efficiency of 0.7% under AM 1.5 conditions. Methods to further improve the technological process are proposed. © 2010 Elsevier B.V.

Nanostructured polymer-based solar cells (PSCs) have emerged as a promising low-cost alternative to conventional inorganic photovoltaic devices and are now a subject of intensive research both in academia and industry. For PSCs to become practical efficient devices, several issues should still be addressed, including further understanding of their operation and stability, which in turn are largely determined by the morphological organisation in the photoactive layer. The latter is typically a few hundred nanometres thick film and is a blend composed of two materials: the bulk heterojunction consisting of the electron donor and the electron acceptor. The main requirements for the morphology of efficient photoactive layers are nanoscale phase segregation for a high donor/acceptor interface area and hence efficient exciton dissociation, short and continuous percolation pathways of both components leading through the layer thickness to the corresponding electrodes for efficient charge transport and collection, and high crystallinity of both donor and acceptor materials for high charge mobility. In this paper, we review recent progress of our understanding on how the efficiency of a bulk heterojunction PSC largely depends on the local nanoscale volume organisation of the photoactive layer.

The effect of the molecular weight of poly[9,9-didecanefluorene-alt-(bis-thienylene) benzothiadiazole] (PF10TBT) on the photovoltaic performance of fullerene-based bulk heterojunction solar cells is investigated. An increase in molecular weight of two orders of magnitude results in a 30% increase of the short-circuit current and a rise of the fill factor from 0.45 to 0.63. Electron and hole transport are found to be virtually unaffected by changing molecular weight, which means that space-charge effects do not play a role in low molecular weight devices. Using optical modeling and numerical device simulations, we demonstrate that at low molecular weight the efficiency is mainly limited by a short lifetime of bound electron-hole pairs. This short lifetime prohibits efficient dissociation and is attributed to a deficiency in phase separation for low molecular weights. (C) 2009 Elsevier B.V. All rights reserved.

The performance of polymer solar cells (PSCs) strongly depends on the three-dimensional morphological organization of the compounds within the bulk heterojunction active layer. Donor and acceptor materials should form co-continuous networks with nanoscale phase separation to sustain effective dissociation of excitons into free electrons and holes at the donor/acceptor interface and to guarantee fast charge carrier transport from any place in the photoactive layer to the corresponding electrodes. Here, we describe applications of the technique of electron tomography to directly visualize with nanometre resolution and study in detail the 3D organization in the photoactive layers of PSCs, with the aim of identifying the critical morphology parameters contributing to high efficiency of bulk heterojunction systems. © 2009 The Royal Society of Chemistry

We have used optical modeling to calculate whether optical absorption and corresponding current densities in solar cells consisting of PF10TBT:PCBM (1:4) can be enhanced, either in single junctions by applying optical spacers or by going to a tandem structure. The current densities are calculated from the optical absorption using experimentally determined IQE values. When an optical spacer is used, the thickness of the transparent electron transport layer (ETL) and hole transport layer (HTL) is very important. The absorption, and thus current density, in a single junction solar cell could be enhanced by 10% by reducing the HTL (PEDOT) thickness and by inserting a thin ETL (30 nm ZnO). The current density in a tandem consisting of two PF10TBT:PCBM blend layers is strongly dependent on the thickness of these blend layers. An increase of 20% is possible for a layer combination of 150 nm and 250 nm, combined with appropriate ETL and HTL layer thicknesses, and assuming no further losses.

A fullerene bisadduct can enhance the efficiency of polymer:fullerene bulk heterojunction solar cells. The bisadduct has a LUMO that is 100 meV higher compared to that of [6,6]-phenyl C-61 butyric acid methyl ester (PCBM). This increases the open-circuit voltage of polymer: fullerene bulk heterojunction solar cells based on poly(3-hexylthiophene) and bisadduct PCBM to 0.73 V, while maintaining high fill factors and currents.

The electro-optical properties of thin films of electron donor-acceptor blends of a fluorene copolymer (PF10TBT) and a fullerene derivative (PCBM) were studied. Transmission electron microscopy shows that in these films nanocrystalline PCBM clusters are formed at high PCBM content. For all concentrations, a charge transfer (CT) transition is observed with absorption spectroscopy, photoluminescence, and electroluminescence. The CT emission is used as a probe to investigate the dissociation of CT excited states at the donor-acceptor interface in photovoltaic devices, as a function of an applied external electric field and PCBM concentration. We find that the maximum of the CT emission shifts to lower energy and decreases in intensity with higher PCBM content. We explain the red shift of the emission and the lowering of the open-circuit voltage (VOC) of photovoltaic devices prepared from these blends with the higher relative permittivity of PCBM (εr = 4.0) compared to that of the polymer (εr = 3.4), stabilizing the energy (ECT) of CT states and of the free charge carriers in blends with higher PCBM concentration. We show that the CT state has a short decay time (τ = ca. 4 ns) that is reduced by the application of an external electric field or with increasing PCBM content. The field-induced quenching can be explained quantitatively with the Onsager-Braun model for the dissociation of the CT states when including a high electron mobility in nanocrystalline PCBM clusters. Furthermore, photoinduced absorption spectroscopy shows that increasing the PCBM concentration reduces the yield of neutral triplet excitons forming via electron-hole recombination, and increases the lifetime of radical cations. The presence of nanocrystalline domains with high local carrier mobility of at least one of the two components in an organic heterojunction may explain efficient dissociation of CT states into free charge carriers. © 2008 American Chemical Society.

This paper gives an overview of the status of photovoltaic devices based on blends of semiconducting polymers. The polymer blends form the bulk heterojunction in these photovoltaic devices. The fundamental mechanisms governing the performance of these devices are discussed as well as the specificities of these all-polymer solar cells. The morphology of the polymer blend layer is expected to influence the device performance of these bulk heterojunctions. An overview is presented of factors that influence the morphology of the active layer of polymer blend photovoltaic devices together with a summary of tools available to study the structure of this layer. An advanced electron microscopy technique is applied to study the morphology of polymer blends of MDMO-PPV and PCNEPV with differing molecular weights. It is shown that the molecular weight of the polymer influences the typical domain size from � 200nm down to less than 5nm in these bulk heterojunction PV devices. No strong relation is observed between the typical length scale of the phase separated domains and the measured external quantum efficiency, indicating that the phases are intermixed. Copyright # 2007 John Wiley & Sons, Ltd.