Nowadays the major factors determining commercialization of lead halide perovskite photovoltaic technology are shifting from solar cell performance to stability, reproducibility, up-scaling, and in particular the concern of Pb leakage during solar cell operation. Here we simulate a realistic scenario that the perovskite solar modules with different encapsulation methods are damaged to a typical extent by mechanical impact (according to the modified FM 44787 standard) and quantitatively measure the lead leakage rates from the damaged modules. We demonstrate that an epoxy resin (ER) based encapsulation method reduces the Pb leakage rate by a factor of 375 compared to the encapsulation method using a glass cover with the UV-resin cured at the module edges. The excellent Pb leakage prevention characteristics is due to the self-healing property of ER and increased mechanical strength. These findings strongly suggest lead halide perovskite photovoltaic products can be used with minimal Pb leakage if appropriate encapsulation is employed.

Upscaling of perovskite solar cells to module scale and affording long-term stability have been recognized as the most important challenges for commercialization of this emerging photovoltaic technology. In a perovskite solar module (PSM), each interface within the device contributes to the efficiency and stability. Here, we employ a holistic interface stabilization strategy by modifying all the relevant layers and interfaces, namely the perovskite layer, charge transporting layers and the device encapsulation to improve the efficiency and stability of PSMs. The treatments were selected to be compatible with low-temperature scalable processing and the module scribing steps. Our unencapsulated PSM achieved a reverse-scan efficiency of 16.6% with a designated area of 22.4 cm 2 . The encapsulated PSM retained approximately 86% 2 of the initial performance after continuous operation for 2000 h under AM 1.5G light illumination, with translates into a T 90 lifetime of 1570 h and an estimated T 80 lifetime of 2680 h.

An amino‐functionalized copolymer with a conjugated backbone composed of fluorene, naphthalene diimide, and thiophene spacers (PFN‐2TNDI) is introduced as an alternative electron transport layer (ETL) to replace the commonly used [6,6]‐Phenyl‐C61‐butyric acid methyl ester (PCBM) in the p–i–n planar‐heterojunction organometal trihalide perovskite solar cells. A combination of characterizations including photoluminescence (PL), time‐resolved PL decay, Kelvin probe measurement, and impedance spectroscopy is used to study the interfacial effects induced by the new ETL. It is found that the amines on the polymer side chains not only can passivate the surface traps of perovskite to improve the electron extraction properties, they also can reduce the work function of the metal cathode by forming desired interfacial dipoles. With these dual functionalities, the resulted solar cells outperform those based on PCBM with power conversion efficiency (PCE) increased from 12.9% to 16.7% based on PFN‐2TNDI. In addition to the performance enhancement, it is also found that a wide range of thicknesses of the new ETL can be applied to produce high PCE devices owing to the good electron transport property of the polymer, which offers a better processing window for potential fabrication of perovskite solar cells using large‐area coating method.

The contact between the n-type interlayer and the donor provides an extra interface for charge dissociation.

Perovskite solar cells (PSCs) have attracted great attention in the past few years due to their rapid increase in efficiency and low‐cost fabrication. However, instability against thermal stress and humidity is a big issue hindering their commercialization and practical applications. Here, by combining thermally stable formamidinium–cesium‐based perovskite and a moisture‐resistant carbon electrode, successful fabrication of stable PSCs is reported, which maintain on average 77% of the initial value after being aged for 192 h under conditions of 85 °C and 85% relative humidity (the “double 85” aging condition) without encapsulation. However, the mismatch of energy levels at the interface between the perovskite and the carbon electrode limits charge collection and leads to poor device performance. To address this issue, a thin‐layer of poly(ethylene oxide) (PEO) is introduced to achieve improved interfacial energy level alignment, which is verified by ultraviolet photoemission spectroscopy measurements. Indeed as a result, power conversion efficiency increases from 12.2% to 14.9% after suitable energy level modification by intentionally introducing a thin layer of PEO at the perovskite/carbon interface.

An upscalable perovskite film deposition method combining raster ultrasonic spray coating and chemical vapor deposition is reported. This method overcomes the coating size limitation of the existing stationary spray, single‐pass spray, and spin‐coating methods. In contrast with the spin‐coating method (>90% Pb waste), negligible Pb waste during PbI2 deposition makes this method more environmentally friendly. Outstanding film uniformity across the entire area of 5 cm × 5 cm is confirmed by both large‐area compatible characterization methods (electroluminescence and scattered light imaging) and local characterization methods (atomic force microscopy, scanning electron microscopy, photoluminescence mapping, UV–vis, and X‐ray diffraction measurements on multiple sample locations), resulting in low solar cell performance decrease upon increasing device area. With the FAPb(I0.85Br0.15)3 (FA = formamidinium) perovskite layer deposited by this method, champion solar modules show a power conversion efficiency of 14.7% on an active area of 12.0 cm2 and an outstanding shelf stability (only 3.6% relative power conversion efficiency decay after 3600 h aging). Under continuous operation (1 sun light illumination, maximum power point condition, dry N2 atmosphere with <5% relative humidity, no encapsulation), the devices show high light‐soaking stability corresponding to an average T80 lifetime of 535 h on the small‐area solar cells and 388 h on the solar module.

Perovskite solar cells have emerged as the next-generation high-efficiency solar cell, but their absorption is mostly limited to the visible (vis) range. One possible solution is to integrate near-infrared (NIR)-to-vis photon upconversion (UC). Herein, we show the first example of endowing perovskite solar cells with NIR sensitivity by using solid films showing NIR-to-vis UC based on triplet-triplet annihilation (TTA). A high TTA-UC efficiency of 4.1 � 0.3 % at an excitation intensity of 125 W/cm 2 is achieved by sensitizing a rubrene (acceptor) triplet with an osmium (Os) complex donor having singlet-to-triplet (SÀ T) absorption in the NIR range, and by increasing the fluorescence quantum yield through energy harvesting to a highly fluorescent collector. In particular, our spectroscopic studies indicate that the upconverted acceptor singlet energy is almost selectively transferred to the collector rather than being quenched by the donor. By attaching the TTA-UC film behind a semi-transparent perovskite solar cell, a photocurrent generation is observed under excitation at 938 nm.

In the application of traditional bulk heterojunction polymer solar cells, to prevent the etching of ITO by the acidic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and thereby improve the device stability, pH-neutral PEDOT:PSS is introduced as the hole transport layer (HTL). After treating the neutral PEDOT:PSS with UV-ozone and with an oxygen plasma, the average power conversion efficiency (PCE) of the device increases from 3.44% to 6.60%. Such surface treatments reduce the energy level offset between the HTL and the active layer, which increases the open circuit voltage and enhances hole transportation, leading to the PCE improvement. Moreover, the devices with the neutral PEDOT:PSS HTL are more stable in air than those with the acidic PEDOT:PSS HTL. The PCE of the devices with the acidic PEDOT:PSS HTL decreases by 20% after 7 days and 45% after 50 days under ambient conditions, whereas the PCE of the devices with the pH-neutral PEDOT:PSS HTL decreases by only 9 and 20% after 7 and 50 days, respectively. X-ray photoelectron spectroscopy shows that the acidic PEDOT:PSS etches the indium from the indium-tin-oxide (ITO) electrode, which is responsible for the degradation of the device. In comparison, the diffusion of the indium is much slower in the devices with the pH-neutral PEDOT:PSS HTL.