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Development of lead-free inorganic perovskite material, such as Cs2AgBiBr6, is of great importance to solve the toxicity and stability issues of traditional lead halide perovskite solar cells. However, due to a wide bandgap of Cs2AgBiBr6 film, its light absorption ability is largely limited and the photoelectronic conversion efficiency is normally lower than 4.23%. In this text, by using a hydrogenation method, the bandgap of Cs2AgBiBr6 films could be tunable from 2.18 eV to 1.64 eV. At the same time, the highest photoelectric conversion efficiency of hydrogenated Cs2AgBiBr6 perovskite solar cell has been improved up to 6.37% with good environmental stability. Further investigations confirmed that the interstitial doping of atomic hydrogen in Cs2AgBiBr6 lattice could not only adjust its valence and conduction band energy levels, but also optimize the carrier mobility and carrier lifetime. All these works provide an insightful strategy to fabricate high performance lead-free inorganic perovskite solar cells. Though inorganic perovskites are an attractive, non-toxic and stable alternative to organic-inorganic halide perovskite solar cells, realizing efficient devices remains a challenge. Here, the authors report hydrogenated lead-free inorganic perovskite solar cells with enhanced power conversion efficiency. [ABSTRACT FROM AUTHOR]

Theoretical studies have shown that surface terminations, such as MAI or PbI layers, greatly affect the environmental stability of organic–inorganic perovskite. However, until now, there has been little effort to experimentally detect the existence of MAI or PbI terminations on MAPbI3 grains, let alone disclose their effects on the humidity degradation pathway of perovskite solar cell. Here, we successfully modified and detected the surface terminations of MAI and PbI species on polycrystalline MAPbI3 films. MAI‐terminated perovskite film followed the moisture degradation process from MAPbI3 to hydrate MAPbI3⋅H2O and then into PbI2, with penetration of water molecules being the main driving force leading to the degradation of MAPbI3 layer by layer. In contrast, for the PbI‐terminated perovskite film in a humid atmosphere, a deprotonation degradation pathway was confirmed, in which the film preferentially degraded directly from MAPbI3 into PbI2, here the iodine defects played a key role in promoting the dissociation of water molecules into OH− and further catalyzing the decomposition of perovskite. [ABSTRACT FROM AUTHOR]

Theoretical studies have shown that surface terminations, such as MAI or PbI layers, greatly affect the environmental stability of organic-inorganic perovskite. However, until now, there has been little effort to experimentally detect the existence of MAI or PbI terminations on MAPbI 3 grains, let alone disclose their effects on the humidity degradation pathway of perovskite solar cell. Here, we successfully modified and detected the surface terminations of MAI and PbI species on polycrystalline MAPbI 3 films. MAI-terminated perovskite film followed the moisture degradation process from MAPbI 3 to hydrate MAPbI 3 ⋅H 2 O and then into PbI 2 , with penetration of water molecules being the main driving force leading to the degradation of MAPbI 3 layer by layer. In contrast, for the PbI-terminated perovskite film in a humid atmosphere, a deprotonation degradation pathway was confirmed, in which the film preferentially degraded directly from MAPbI 3 into PbI 2 , here the iodine defects played a key role in promoting the dissociation of water molecules into OH - and further catalyzing the decomposition of perovskite., (© 2020 Wiley-VCH GmbH.)