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Kinetic Stabilization of the Sol–Gel State in Perovskites Enables Facile Processing of High‐Efficiency Solar Cells
Author(s) -
Wang Kai,
Tang MingChun,
Dang Hoang X.,
Munir Rahim,
Barrit Dounya,
De Bastiani Michele,
Aydin Erkan,
Smilgies DetlefM.,
Wolf Stefaan,
Amassian Aram
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201808357
Subject(s) - halide , perovskite (structure) , materials science , crystallization , energy conversion efficiency , photovoltaic system , phase (matter) , chemical engineering , nanotechnology , inorganic chemistry , optoelectronics , chemistry , organic chemistry , ecology , engineering , biology
Perovskite solar cells increasingly feature mixed‐halide mixed‐cation compounds (FA 1− x − y MA x Cs y PbI 3− z Br z ) as photovoltaic absorbers, as they enable easier processing and improved stability. Here, the underlying reasons for ease of processing are revealed. It is found that halide and cation engineering leads to a systematic widening of the anti‐solvent processing window for the fabrication of high‐quality films and efficient solar cells. This window widens from seconds, in the case of single cation/halide systems (e.g., MAPbI 3 , FAPbI 3 , and FAPbBr 3 ), to several minutes for mixed systems. In situ X‐ray diffraction studies reveal that the processing window is closely related to the crystallization of the disordered sol–gel and to the number of crystalline byproducts; the processing window therefore depends directly on the precise cation/halide composition. Moreover, anti‐solvent dripping is shown to promote the desired perovskite phase with careful formulation. The processing window of perovskite solar cells, as defined by the latest time the anti‐solvent drip yields efficient solar cells, broadened with the increasing complexity of cation/halide content. This behavior is ascribed to kinetic stabilization of sol–gel state through cation/halide engineering. This provides guidelines for designing new formulations, aimed at formation of the perovskite phase, ultimately resulting in high‐efficiency perovskite solar cells produced with ease and with high reproducibility.