Defect chemistry analysis on CH3NH3PbI3 toward conductivity control of lead-halide perovskites
Yuiga Nakamura a, Tomonori Matsushita b c, Shu Yamaguchi a, Takashi Kondo a c
a University of Tokyo, Japan, Japan
b University of Tokyo, Japan, Japan
c Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Japan, Japan
NIPHO
Proceedings of International Conference on Perovskite Thin Film Photovoltaics, Photonics and Optoelectronics (ABXPV18PEROPTO)
Perovskite Thin Film Photovoltaics (ABXPV18). 27-28 Feb
Rennes, France, 2018 February 27th - March 1st
Organizer: Jacky Even
Poster, Yuiga Nakamura, 093
Publication date: 11th December 2017

CH3NH3PbI3 polycrystalline thin films have been intensively investigated as light-absorbing layers in solution-processable perovskite solar cells. It has been pointed out that iodide ions diffusing via vacancies are responsible for large ionic conduction and for I-V hysteresis in part. We propose to control iodide ion vacancies in CH3NH3PbI3 by fabricating polycrystalline films using vacuum co-evaporation of HI, CH3NH2 and PbI2. In this presentation, we report on iodide ion vacancy and electron/hole densities in CH3NH3PbI3 thin films based on a defect chemistry analysis. We show by the simulation that concentration of the vacancies can be controlled by activities (partial pressures) of HI and CH3NH2 gasses in the co-evaporation process. In addition, conductivities can be controlled through designed electron/hole densities by changing the activities. We also present preliminary results of a ternary co-evaporation experiment using HI and CH3NH2 gas sources and a PbI2 solid source. We introduced a ternary vacuum evaporation system and successfully fabricated (110)-oriented CH3NH3PbI3 thin films.

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