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Improving the performance of solar modules requires the implementation of both spectral and directional irradiance optimization. The performance of bifacial four-terminal tandem minimodules with a 100 cm2 area is reported, both indoor and outdoor measurements. We demonstrate a 24.5 mW/cm2 (bifacial irradiance 200 W/m2) bifacial tandem power density, measured according to a tandem adapted IEC60904-1-2 protocol, which constitutes a 3 mW/cm2 gain with respect to monofacial use. In addition, we show that in outdoor measurements bifacial four terminal tandems outperform identical monofacial four terminal tandems by 26% on average, depending on incident angle, injection level and temperature, in a 10% albedo environment. The average gain is higher for outdoor performance than for indoor performance, due to variations in relative rear irradiance.

Single junction crystalline silicon (c‐Si) solar cells are reaching their practical efficiency limit whereas perovskite/c‐Si tandem solar cells have achieved efficiencies above the theoretical limit of single junction c‐Si solar cells. Next to low‐thermal budget silicon heterojunction architecture, high‐thermal budget carrier‐selective passivating contacts (CSPCs) based on polycrystalline‐SiOx (poly‐SiOx) also constitute a promising architecture for high efficiency perovskite/c‐Si tandem solar cells. In this work, we present the development of c‐Si bottom cells based on high temperature poly‐SiOx CSPCs and demonstrate novel high efficiency four‐terminal (4T) and two‐terminal (2T) perovskite/c‐Si tandem solar cells. First, we tuned the ultra‐thin, thermally grown SiOx. Then we optimized the passivation properties of p‐type and n‐type doped poly‐SiOx CSPCs. Here, we have optimized the p‐type doped poly‐SiOx CSPC on textured interfaces via a two‐step annealing process. Finally, we integrated such bottom solar cells in both 4T and 2T tandems, achieving 28.1% and 23.2% conversion efficiency, respectively. [ABSTRACT FROM AUTHOR]

Wide bandgap perovskites are being widely studied in view of their potential applications in tandem devices and other semitransparent photovoltaics. Vacuum deposition of perovskite thin films is advantageous as it allows the fabrication of multilayer devices, fine control over thickness and purity, and it can be upscaled to meet production needs. However, the vacuum processing of multicomponent perovskites (typically used to achieve wide bandgaps) is not straightforward, because one needs to simultaneously control several thermal sources during the deposition. Here a simplified dual‐source vacuum deposition method to obtain wide bandgap perovskite films is shown. The solar cells obtained with these materials have similar or even larger efficiency as those including multiple A‐cations, but are much more thermally stable, up to 3500 h at 85 °C for a perovskite with a bandgap of 1.64 eV. With optimized thickness, record efficiency of >19% and semitransparent devices with stabilized power output in excess of 17% are achieved. [ABSTRACT FROM AUTHOR]

Recently perovskite/crystalline Si (cSi) tandem cells draw considerable attention because their high efficiency can reduce the levelized cost of electricity and increase the power density of photovoltaics (PVs) to accelerate the energy transition. While the theoretical limits for tandem cells are well known, the practical limits are less clear. Herein, a new method is presented to calculate the efficiency of a four-terminal (4T) tandem based on the performance of singlejunction perovskite and cSi cells, using their detailed-balance efficiency fraction. This calculation method is validated with experiments on 4T perovskite/cSi tandem cells that provide a maximum efficiency of 28.0% and with the literature data available for similar configurations. A maximum efficiency of about 36% is estimated for 4T perovskite/cSi tandem cells that would use present record perovskite and cSi PV cells. This can be regarded as the practical efficiency limit for 4T perovskite/cSi tandem devices. [ABSTRACT FROM AUTHOR]

Semitransparent perovskite solar cells (ST‐PSCs) are very attractive due to their potential applications in single junctions for building‐integrated photovoltaics (BIPV) and in tandem PV technology using low‐bandgap bottom solar cells. Despite the high efficiency achieved, the ST‐PSCs still suffer low bifaciality, which can limit their overall energy yield for application in BIPV technologies. Furthermore, the knowledge on the long‐term light‐soaking stability of the ST‐PSC from both illumination sides is required to optimize the energy production in the long term. p−i−n ST‐PSCs and semitransparent perovskite solar minimodules with comparable and high efficiencies when illuminated from either the rear or the front sides, resulting in the highest reported bifaciality factor of 97%, are demonstrated. A bifacial equivalent power output of 21.3 W m−2 is achieved for ST‐PSCs under 1 sun illumination on the front side, while using a white back reflector from the rear side with 33.5% reflected albedo. However, the side of illumination has a big impact on the light‐soak stability of the ST‐PSCs. It is observed that the ST‐PSC provides more stable output power under illumination from the rear side (n‐side) of the stack. [ABSTRACT FROM AUTHOR]

Improving the performance of solar modules requires the implementation of both spectral and directional irradiance optimization. The performance of bifacial four-terminal tandem minimodules with a 100 cm2 area is reported, both indoor and outdoor measurements. We demonstrate a 24.5 mW/cm2 (bifacial irradiance 200 W/m2) bifacial tandem power density, measured according to a tandem adapted IEC60904-1-2 protocol, which constitutes a 3 mW/cm2 gain with respect to monofacial use. In addition, we show that in outdoor measurements bifacial four terminal tandems outperform identical monofacial four terminal tandems by 26% on average, depending on incident angle, injection level and temperature, in a 10% albedo environment. The average gain is higher for outdoor performance than for indoor performance, due to variations in relative rear irradiance. [ABSTRACT FROM AUTHOR]

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 <200 °C. 100‐nm thick films feature a sheet resistance of 21 Ω◻−1 with electron mobilities ≈70 cm2 V−1s−1. PLD‐grown IZrO is applied as rear electrode in efficient semi‐transparent halide perovskite solar cells leading to the improved stabilized maximum power point efficiency (15.1%) as compared to the cells with sputtered ITO electrodes (11.9%). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The studies of the electro-optical properties of thin films of electron donor-acceptor blend of a fluorene copolymer (PF10TBT) and a fullerene derivative (PCBM) is reported. The results obtained from photoinduced absorption spectroscopy showed that increasing the PCBM concentration reduces the yields of neutral triplet excitons formed via electron-hole recombination, and increases the lifetime of radical cations.

Abstract: 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%. [ABSTRACT FROM AUTHOR]

Perovskite solar cells employing poly(3,4-ethylenedioxythiophene) (PEDOT) as hole transport layer on top of methylammonium lead halide are reported, yielding a power conversion efficiency of 11% and a 6% stabilized power output. An atomic layer deposition assisted interface architectural approach is adopted to fabricate the n-i-p perovskite/PEDOT devices. The results present a promising next step toward efficient low-cost perovskite-based photovoltaic technology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Indium-tin-oxide-free (ITO-free) polymer solar cells with composite electrodes containing current-collecting grids and a semitransparent poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) (PEDOT:PSS) conductor are demonstrated. The up-scaling of the length of the solar cell from 1 to 6 cm and the effect of the grid line resistance are explored for a series of devices. Laser-beam-induced current (LBIC) mapping is used for quality control of the devices. A theoretical modeling study is presented that enables the identification of the most rational cell dimension for the grids with different resistances. The performance of ITO-free organic solar cells with different dimensions and different electrode resistances are evaluated for different light intensities. The current generation and electric potential distribution are found to not be uniformly distributed in large-area devices at simulated 1 Sun illumination. The generated current uniformity increases with decreasing light intensities. [ABSTRACT FROM AUTHOR]

Five different indium-tin-oxide free (ITO-free) polymer solar cell architectures provided by four participating research institutions that all presented a laboratory cell performance sufficient for use in mobile and information and communication technology (ICT) were evaluated based on photovoltaic performance and lifetime tests according to the ISOS protocols. The comparison of the different device architectures was performed using the same active material (P3HT: PCBM) and tested against an ITO-based reference device. The active area was 1 cm2 and rigid glass or flexible polyester substrates were employed. The performance results were corroborated by use of a round robin methodology between the four participating laboratories (DTU/DK, ECN/NL, Frauenhofer ISE/DE, and the Holst Centre/NL), while the lifetime testing experiments were carried out in only one location (DTU). Five different lifetime testing experiments were carried out for a minimum of 1000 h: (1) shelf life (according to ISOS-D-1); (2-3) stability under continuous 1 sun illumination (1000 Wm−2, AM1.5G) at low (37 ± 3°C) and high (80 ± 5°C) temperatures (according to ISOS-L-1 and ISOS-L-2); (4) stability under continuous low-light conditions at 0.1 sun (100 Wm−2, AM1.5G, 32°C) (according to ISOS-LL); (5) continuous illumination (670 Wm−2, AM1.5G) at high temperature (65°C) and high humidity (50% RH) (according to ISOS-L-3). Finally, the upscaling compatibility of these device architectures based on the device photovoltaic behavior, stability and scalability were identified and we confirm that an architecture that presents a high score in only one aspect of the solar cell performance is not sufficient to justify an investment in upscaling. Many will require further technical development. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 944-954, 2013 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An organic bulk heterojunction photovoltaic device based on a blend of two conjugated polymers, a polyphenylenevinylene as the electron donor and a red emitting polyfluorene as the acceptor, is presented with a maximum external quantum efficiency of 52% at 530 nm and a power conversion efficiency, measured under AM1.5G, 100 mW/cm2 conditions, of 1.5% on an active area of 0.36 cm2. [ABSTRACT FROM AUTHOR]

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. Atmospheric pressure spatial atomic layer technique (s‐ALD) has been adopted to introduce a ZnO buffer layer in the p‐i‐n planar perovskite solar cell architecture. The s‐ALD layer successfully prevents damages during ITO sputtering deposition, enabling the fabrication of efficient and stable semitransparent bifacial perovskite solar cells. [ABSTRACT FROM AUTHOR]

A two-step sequential deposition method has been applied to prepare the solar cells with two types of perovskites Cs 0.15 FA 0.85 Pb(I 0.95 Cl 0.05) 3 and Cs 0.15 FA 0.85 Pb(I 0.95 Br 0.05) 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. [Display omitted] • The sequential deposition method was applied to prepare perovskite solar cells. • The dual cation (2C) perovskites were investigated. • Different sources of Br and Cl atoms were used for synthesis of perovskites. [ABSTRACT FROM AUTHOR]

In this work, we present an extensive characterization of plasma-assisted atomic-layer-deposited SnO 2 layers, with the aim of identifying key material properties of SnO 2 to serve as an efficient electron transport layer in perovskite solar cells (PSCs). Electrically resistive SnO 2 films are fabricated at 50 °C, while a SnO 2 film with a low electrical resistivity of 1.8 × 10 -3 Ω cm, a carrier density of 9.6 × 10 19 cm -3 , and a high mobility of 36.0 cm 2 /V s is deposited at 200 °C. Ultraviolet photoelectron spectroscopy indicates a conduction band offset of ∼0.69 eV at the 50 °C SnO 2 /Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I 2.7 Br 0.3 ) interface. In contrast, a negligible conduction band offset is found between the 200 °C SnO 2 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 SnO 2 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 SnO 2 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 SnO 2 shows a decrease in PCE of approximately 50%.

Transmission electron microscopy and electron diffraction are used to study the changes in morphology of composite films of poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM) in bulk heterojunction solar cells. Thermal annealing produces and stabilizes a nanoscale interpenetrating network with crystalline order for both components. P3HT forms long, thin conducting nanowires in a rather homogeneous, nanocrystalline PCBM film. Both the improved crystalline nature of films and increased but controlled demixing between the two constitutes therein after annealing explains the considerable increase of the power conversion efficiency observed in these devices.