Avoiding buried voids The buried interfaces of perovskite solar cells are difficult to alter after synthesis. During manufacture, Chen et al . removed perovskite films with dimethyl sulfoxide solvent from the hole-transfer layer and observed a substantial void fraction that degraded film performance. Replacing most of the dimethyl sulfoxide with carbohydrazide, a lead-coordinating compound with a much higher boiling point, eliminated voids. Such solar cells maintained high power conversion efficiency after 550 hours of operation at 60°C. —PDS

The efficiencies of small-pixel perovskite photovoltaics have increased to above 24%, while most reported fabrication methods cannot be transferred to scalable manufacturing process. Here, we report a method of fast blading large-area perovskite films at an unprecedented speed of 99 mm/s under ambient conditions by tailoring solvent coordination capability. Combing volatile noncoordinating solvents to Pb2+ and low-volatile, coordinating solvents achieves both fast drying and large perovskite grains at room temperature. The reproducible fabrication yields a certified module efficiency of 16.4%, with an aperture area of 63.7 cm2. This method can be applied for various perovskite compositions. The perovskite modules also show a small temperature coefficient of −0.13%/°C and nearly fully recoverable efficiency after 58 cycles of shading, much better than commercial silicon and thin-film solar modules.

A new monolithic perovskite/silicon tandem solar cell architecture is proposed based on double-side-textured silicon cells with sub-micrometer pyramids. These pyramids are rough enough to scatter light within silicon nearly as efficiently as large pyramids but smooth enough to solution process a perovskite film. A bladecoated perovskite film planarizes the textured silicon cell. With a textured lightscattering layer added to the top to reduce front-surface reflectance, a monolithic perovskite/silicon tandem cell reaches an efficiency of 26%.

The power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) are already higher than that of other thin film technologies, but laboratory cell-fabrication methods are not scalable. Here, we report an additive strategy to enhance the efficiency and stability of PSCs made by scalable blading. Blade-coated PSCs incorporating bilateral alkylamine (BAA) additives achieve PCEs of 21.5 (aperture, 0.08 cm2) and 20.0% (aperture, 1.1 cm2), with a record-small open-circuit voltage deficit of 0.35 V under AM1.5G illumination. The stabilized PCE reaches 22.6% under 0.3 sun. Anchoring monolayer bilateral amino groups passivates the defects at the perovskite surface and enhances perovskite stability by exposing the linking hydrophobic alkyl chain. Grain boundaries are reinforced by BAA and are more resistant to mechanical bending and electron beam damage. BAA improves the device shelf lifetime to >1000 hours and operation stability to >500 hours under light, with 90% of the initial efficiency retained.

Perovskite materials are good candidates for flexible photovoltaic applications due to their strong absorption and low-temperature processing, but efficient flexible perovskite modules have not been realized yet. Here, we demonstrate a record efficiency flexible perovskite solar module by blade coating high-quality perovskite films on flexible Corning® Willow® Glass using additive engineering. Ammonium chloride (NH 4 Cl) is added into perovskite precursor solution to retard the nucleation which prevents forming voids at the interface of perovskite and glass. The addition of NH 4 Cl also suppresses the formation of PbI 2 reduces the trap density in the perovskite films. The implementation of NH 4 Cl enabled fabricating single junction flexible perovskite solar devices with an efficiency of 19.72% on the small area cells and a record aperture efficiency of 15.86% on the modules with an area of 42.9 cm 2. This work provides a simple way to scale up high-efficiency flexible perovskite modules for various applications.

Endured, low‐cost, and high‐performance flexible perovskite solar cells (PSCs) featuring lightweight and mechanical flexibility have attracted tremendous attention for portable power source applications. However, flexible PSCs typically use expensive and fragile indium–tin oxide as transparent anode and high‐vacuum processed noble metal as cathode, resulting in dramatic performance degradation after continuous bending or thermal stress. Here, all‐carbon‐electrode‐based flexible PSCs are fabricated employing graphene as transparent anode and carbon nanotubes as cathode. All‐carbon‐electrode‐based flexible devices with and without spiro‐OMeTAD (2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene) hole conductor achieve power conversion efficiencies (PCEs) of 11.9% and 8.4%, respectively. The flexible carbon‐electrode‐based solar cells demonstrate superior robustness against mechanical deformation in comparison with their counterparts fabricated on flexible indium–tin oxide substrates. Moreover, all carbon‐electrode‐based flexible PSCs also show significantly enhanced stability compared to the flexible devices with gold and silver cathodes under continuous light soaking or 60 °C thermal stress in air, retaining over 90% of their original PCEs after 1000 h. The promising durability and stability highlight that flexible PSCs are fully compatible with carbon materials and pave the way toward the realization of rollable and low‐cost flexible perovskite photovoltaic devices.

NiO is a promising hole-transporting material for perovskite solar cells due to its high hole mobility, good stability, and easy processability. In this work, we employed a simple solution-processed NiO film as the hole-transporting layer in perovskite solar cells. When the thickness of the perovskite layer increased from 270 to 380 nm, the light absorption and photogenerated carrier density were enhanced and the transporting distance of electron and hole would also increase at the same time, resulting in a large charge transfer resistance and a long hole-extracted process in the device, characterized by the UV-vis, photoluminescence, and electrochemical impedance spectroscopy spectra. Combining both of these factors, an optimal thickness of 334.2 nm was prepared with the perovskite precursor concentration of 1.35 M. Moreover, the optimal device fabrication conditions were further achieved by optimizing the thickness of NiO hole-transporting layer and PCBM electron selective layer. As a result, the best power conversion efficiency of 15.71% was obtained with a J of 20.51 mA·cm, a V of 988 mV, and a FF of 77.51% with almost no hysteresis. A stable efficiency of 15.10% was caught at the maximum power point. This work provides a promising route to achieve higher efficiency perovskite solar cells based on NiO or other inorganic hole-transporting materials.

With power conversion efficiencies now reaching 24.2%, the major factor limiting efficient electricity generation using perovskite solar cells (PSCs) is their long‐term stability. In particular, PSCs have demonstrated rapid degradation under illumination, the driving mechanism of which is yet to be understood. It is shown that elevated device temperature coupled with excess charge carriers due to constant illumination is the dominant force in the rapid degradation of encapsulated perovskite solar cells under illumination. Cooling the device to 20 °C and operating at the maximum power point improves the stability of CH3NH3PbI3 solar cells over 100× compared to operation under open circuit conditions at 60 °C. Light‐induced strain originating from photothermal‐induced expansion is also observed in CH3NH3PbI3, which excludes other light‐induced‐strain mechanisms. However, strain and electric field do not appear to play any role in the initial rapid degradation of CH3NH3PbI3 solar cells under illumination. It is revealed that the formation of additional recombination centers in PSCs facilitated by elevated temperature and excess charge carriers ultimately results in rapid light‐induced degradation. Guidance on the best methods for measuring the stability of PSCs is also given.