title: Dissociation of Methylammonium Cations in Hybrid Organic-Inorganic Perovskite Solar Cells.
abstract: Organic-inorganic lead perovskites have shown great promise as photovoltaic materials, and within this class of materials (CH3NH3)PbI3-xClx is of particular interest. Herein we use soft X-ray spectroscopy and density functional theory calculations to demonstrate that the methylammonium cations in a typical photovoltaic layer may dissociate into a metastable arrangement of CH3I-Pb2 defects and trapped NH3. The possibility that other metastable configurations of the organic components in (CH3NH3)PbI3-xClx is rarely considered but adds an entirely new dimension in understanding the charge trapping, ionic transport, and structural degradation mechanisms in these materials. Understanding the influence of these other configurations is of critical importance for further improving the performance of these photovoltaics.
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123 China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Xu
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123 China.
authors.forename: Lijia
authors.initials: L
authors.lastname: Liu
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123 China.
authors.forename: Linju
authors.initials: L
authors.lastname: Yang
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123 China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Shen
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123 China.
authors.forename: Baoquan
authors.initials: B
authors.lastname: Sun
authors.affiliation: Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123 China.
authors.forename: John A
authors.initials: JA
authors.lastname: McLeod
keywords: Methylammonium lead halide perovskite; defect; photovoltaic; x-ray absorption spectroscopy; x-ray emission spectroscopy