A Thermodynamically Favored Crystal Orientation in Mixed Formamidinium/Methylammonium Perovskite for Efficient Solar Cells

Ziqi Xu, Zonghao Liu, Nengxu Li, Gang Tang, Guanhaojie Zheng, Cheng Zhu, Yihua Chen, Ligang Wang, Yuan Huang, Liang Li, Ning Zhou, Jiawang Hong, Qi Chen, Huanping Zhou*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

113 Citations (Scopus)

Abstract

Crystal orientation has a great impact on the properties of perovskite films and the resultant device performance. Up to now, the exquisite control of crystal orientation (the preferred crystallographic planes and the crystal stacking mode with respect to the particular planes) in mixed-cation perovskites has received limited success, and the underlying mechanism that governs device performance is still not clear. Here, a thermodynamically favored crystal orientation in formamidinium/methylammonium (FA/MA) mixed-cation perovskites is finely tuned by composition engineering. Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently. The preferable growth along the (001) crystal plane, when lying parallel to the substrates, affects their charge transportation and collection properties. Under the optimized condition, the mixed-cation perovskite (FA1–x MAx PbI2.87Br0.13 (Cl)) solar cells deliver a champion power conversion efficiency over 21%, with a certified efficiency of 20.50 ± 0.50%. The present work not only provides a vital step in understanding the intrinsic properties of mixed-cation perovskites but also lays the foundation for further investigation and application in perovskite optoelectronics.

Original languageEnglish
Article number1900390
JournalAdvanced Materials
Volume31
Issue number24
DOIs
Publication statusPublished - 13 Jun 2019

Keywords

  • charge transportation
  • perovskite solar cells
  • preferable orientation
  • surface energy
  • thermodynamics

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