期刊
ACS NANO
卷 9, 期 2, 页码 2088-2101出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn507345e
关键词
mixed halide perovskites; solution processing; solar cells; Raman spectroscopy; charge separation mechanism; density functional theory
类别
资金
- Swedish Energy Agency
- STandUP for Energy Program
- Swedish Research Council (VR)
- Goran Gustafsson Foundation
- Knut and Alice Wallenberg Foundation
- Angpanneforenings Research Foundation
Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide and show remarkably improved charge separation capabilities when chloride and bromide are added. Here we show how halide substitution in OMHPs with the nominal composition CH3NH3PbI2X, where X is I, Br, or Cl, influences the morphology, charge quantum yield, and local interaction with the organic MA cation. X-ray diffraction and photoluminescence data demonstrate that halide substitution affects the local structure in the OMHPs with separate MAPbI3 and MAPbCl(3) phases. Raman spectroscopies as well as theoretical vibration calculations reveal that this at the same time delocalizes the charge to the MA cation, which can liberate the vibrational movement of the MA cation, leading to a more adaptive organic phase. The resonance Raman effect together with quantum chemical calculations is utilized to analyze the change in charge transfer mechanism upon electronic excitation and gives important clues for the mechanism of the much improved photovoltage and photocurrent also seen in the solar cell performance for the materials when chloride compounds are included in the preparation.
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