Spectral Instability of Layered Mixed Halide Perovskites Results from Anion Phase Redistribution and Selective Hole Injection

Yoonseo Nah, Omar Allam, Han Seul Kim, Ji Il Choi, In Soo Kim, Jinwoo Byun, Sang Ouk Kim, Seung Soon Jang, Dong Ha Kim

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Despite the ability to precisely tune their bandgap energies, mixed halide perovskites (MHPs) suffer from significant spectral instability, which obstructs their utilization for the rational design of light-emitting diodes. Here, we investigate the origin of the electroluminescence peak shifts in layered MHPs containing bromide and iodide. X-ray diffraction and steady-state absorption measurements prove effective integration of iodide into the cubic lattice and the spatially uniform distribution of halides in the ambient environment. However, the applied electric field during the device operation is found to drive the systematic halide migration. Quantum mechanical density functional theory calculations reveal that the different activation energies required for directional ion hopping lead to the redistribution of anions. In-depth analyses of the electroluminescence spectra indicate that the spectral shifting rate is dependent on the drift velocity of halides. Finally, it is suggested from our study that the dominant red emission is ascribed to the thermodynamically favorable selective hole injection. Our mechanistic study provides insights into the fundamental reason for the spectral instability of devices based on MHPs.

Original languageEnglish
Pages (from-to)1486-1496
Number of pages11
JournalACS Nano
Volume15
Issue number1
DOIs
StatePublished - 26 Jan 2021

Keywords

  • halide redistribution
  • ion migration
  • mixed halide perovskite
  • perovskite light-emitting diode
  • spectral instability

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