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Electron‐Transport‐Layer‐Assisted Crystallization of Perovskite Films for High‐Efficiency Planar Heterojunction Solar Cells
Author(s) -
Wang YingChiao,
Chang Junwei,
Zhu Liping,
Li Xiaodong,
Song Changjian,
Fang Junfeng
Publication year - 2018
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201706317
Subject(s) - materials science , nucleation , crystallization , perovskite (structure) , chemical engineering , energy conversion efficiency , crystal (programming language) , heterojunction , crystal growth , crystallography , optoelectronics , chemistry , organic chemistry , computer science , engineering , programming language
Crystal engineering of CH 3 NH 3 PbI 3 perovskite materials through template‐directed nucleation and growth on PbI 2 nuclei dispersed in a polar fullerene (C 60 pyrrolidine tris‐acid, CPTA) electron transport layer (ETL) (CPTA:PbI 2 ) is proposed as a route for controlling crystallization kinetics and grain sizes. Chemical analysis of the CPTA:PbI 2 template confirms that CPTA carboxylic acid groups can form a monodentate or bidentate chelate with Pb(II), resulting in a lower nucleation barrier that promotes rapid formation of the tetragonal perovskite phase. Moreover, it is demonstrated that a uniform CH 3 NH 3 PbI 3 film with highly crystalline and large domain sizes can be realized by increasing the spacing between nuclei to retard perovskite crystal growth via careful control of the preferred nucleation site distribution in the CPTA:PbI 2 layer. The improved perovskite morphology possesses a long photoluminescence lifetime and efficient photocarrier transport/separation properties to eliminate the hysteresis effect. The corresponding planar heterojunction photovoltaic yields a high power conversion efficiency (PCE) of 20.20%, with a high fill factor (FF) of 81.13%. The average PCE and FF values for 30 devices are 19.03% ± 0.57% and 78.67% ± 2.13%, respectively. The results indicate that this ETL template‐assisted crystallization strategy can be applied to other organometal halide perovskite‐based systems.