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FA 0.88 Cs 0.12 PbI 3− x (PF 6 ) x Interlayer Formed by Ion Exchange Reaction between Perovskite and Hole Transporting Layer for Improving Photovoltaic Performance and Stability
Author(s) -
Chen Jiangzhao,
Kim SeulGi,
Park NamGyu
Publication year - 2018
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.201801948
Subject(s) - materials science , perovskite (structure) , formamidinium , iodide , analytical chemistry (journal) , hysteresis , ion , energy conversion efficiency , band gap , grain boundary , relative humidity , open circuit voltage , chemical engineering , inorganic chemistry , optoelectronics , voltage , microstructure , condensed matter physics , chemistry , physics , chromatography , quantum mechanics , thermodynamics , engineering , metallurgy
Interface engineering to form an interlayer via ion exchange reaction is reported. A FA 0.88 Cs 0.12 PbI 3 formamidinium (FA) perovskite layer is first prepared, then FAPF 6 solution with different concentrations is spin‐coated on top of the perovskite film, which leads to a partial substitution of iodide by PF 6 − ion. The second phase with nominal composition of FA 0.88 Cs 0.12 PbI 3− x (PF 6 ) x is grown at the grain boundary, which has island morphology and its size depends on the FAPF 6 solution concentration. The lattice is expanded and bandgap is reduced due to inclusion of larger PF 6 − ions. The power conversion efficiency (PCE) is significantly enhanced from 17.8% to 19.3% as a consequence of improved fill factor and open‐circuit voltage ( V oc ). In addition, current–voltage hysteresis is reduced. Post‐treatment with FAPF 6 reduces defect density and enhances carrier lifetime, which is responsible for the improved photovoltaic performance and reduced hysteresis. The unencapsulated device with post‐treated perovskite film demonstrates better stability than the pristine perovskite, where the initial PCE retains over 80% after 528 h exposure under relative humidity of around 50–70% in the dark and 92% after 360 h under one sun illumination.