Published January 1, 2021 | Version v1
Journal article Open

Performance-limiting formation dynamics in mixed-halide perovskites

  • 1. Univ Calif Los Angeles, Dept Chem, Los Angeles, CA 90095 USA
  • 2. Marmara Univ, Dept Phys, TR-34722 Istanbul, Turkey
  • 3. Lawrence Berkeley Natl Lab, Chem Sci Div, Berkeley, CA 94720 USA
  • 4. Lawrence Berkeley Natl Lab, Mat Sci Div, Berkeley, CA 94720 USA
  • 5. Washington State Univ, Ctr Mat Res, Pullman, WA 99164 USA

Description

Wide-bandgap (WBG) mixed-halide perovskites as the front cell absorber are accomplishing perovskite-based tandem solar cells with over 29% power conversion efficiency. However, their large voltage deficits limit their ultimate performance. Only a handful of studies probe the fundamental mechanisms underlying the voltage deficits, which remain an unsolved challenge in the field. In this study, we investigate the formation dynamics and defect physics of WBG mixed-halide perovskites in contrast with their corresponding triiodide-based perovskites. Our results show that the inclusion of bromide introduced a halide homogenization process that occurs during the perovskite growth stage from an initial bromide-rich phase toward the final target stoichiometry. We further elucidated a physical model that correlates the role of bromide with the formation dynamics, defect physics, and eventual optoelectronic properties of the film. This work provides a fundamental and unique perspective toward understanding the performance-limiting factors affecting WBG mixed-halide perovskites.

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