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Controlling the Formation Process of Methylammonium‐Free Halide Perovskite Films for a Homogeneous Incorporation of Alkali Metal Cations Beneficial to Solar Cell Performance
Author(s) -
Zheng Daming,
Zhu Tao,
Yan Yanfa,
Pauporté Thierry
Publication year - 2022
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.202103618
Subject(s) - formamidinium , halide , alkali metal , iodide , crystallinity , perovskite (structure) , inorganic chemistry , materials science , triiodide , crystallization , chemical engineering , annealing (glass) , perovskite solar cell , nucleation , energy conversion efficiency , mineralogy , chemistry , electrolyte , crystallography , dye sensitized solar cell , organic chemistry , composite material , electrode , optoelectronics , engineering
Incorporating multiple cations of the 1A alkali metal column of the periodic table (K + /Rb + /Cs + ) to prepare perovskite films is promising for boosting photovoltaic properties but requires a uniform distribution. The effects of NH 4 Cl additives and alkali metal cations (K + /Rb + /Cs + ) on the one‐step formation process of methylammonium‐free, formamidinium‐based, iodide perovskite films are analyzed in a step‐by‐step manner. NH 4 Cl improves the solubility of PbI 2 in solution by forming an intermediate and then favors the perovskite phase formation. Moreover, during the annealing process, this additive is shown to increase grain size, to improve crystallinity and to suppress PbI 2 formation. K at low concentration is always homogeneously distributed across the film thickness. On the other hand, Cs is more concentrated at the surface and Rb in the depths of pristine films. With NH 4 Cl additives, these two alkali metals are more homogeneously distributed because NH 4 Cl slows down the movement of Cs + and Rb + , it changes the growth direction of the perovskite film, making the overall crystallization quality improved and the distribution more uniform. It results in perovskite films with large monolithic grains. Combined with a perovskite film surface treatment with n‐propylammonium iodide, a high stabilized power conversion efficiency of 22.04% is reached.