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Adverse Effects of Excess Residual PbI 2 on Photovoltaic Performance, Charge Separation, and Trap‐State Properties in Mesoporous Structured Perovskite Solar Cells
Author(s) -
Wang HaoYi,
Hao MingYang,
Han Jun,
Yu Man,
Qin Yujun,
Zhang Pu,
Guo ZhiXin,
Ai XiCheng,
Zhang JianPing
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201605668
Subject(s) - materials science , crystallinity , perovskite (structure) , photovoltaic system , mesoporous material , halide , context (archaeology) , fabrication , chemical engineering , inorganic chemistry , chemistry , composite material , organic chemistry , catalysis , electrical engineering , medicine , paleontology , alternative medicine , pathology , engineering , biology
Organic–inorganic halide perovskite solar cells have rapidly come to prominence in the photovoltaic field. In this context, CH 3 NH 3 PbI 3 , as the most widely adopted active layer, has been attracting great attention. Generally, in a CH 3 NH 3 PbI 3 layer, unreacted PbI 2 inevitably coexists with the perovskite crystals, especially following a two‐step fabrication process. There appears to be a consensus that an appropriate amount of unreacted PbI 2 is beneficial to the overall photovoltaic performance of a device, the only disadvantageous aspect of excess residual PbI 2 being viewed as its insulating nature. However, the further development of such perovskite‐based devices requires a deeper understanding of the role of residual PbI 2 . In this work, PbI 2 ‐enriched and PbI 2 ‐controlled perovskite films, as two extreme cases, have been prepared by modulating the crystallinity of a pre‐deposited PbI 2 film. The effects of excess residual PbI 2 have been elucidated on the basis of spectroscopic and optoelectronic studies. The initial charge separation, the trap‐state density, and the trap‐state distribution have all been found to be adversely affected in PbI 2 ‐enriched devices, to the detriment of photovoltaic performance. This leads to a biphasic recombination process and accelerates the charge carrier recombination dynamics.