Is more Phase Segregation better for mixed halide perovskite devices: Spatial randomness, Ion migration, and Non-radiative recombination

TL;DR

This study investigates how phase segregation, ion migration, and interface effects influence the performance and stability of mixed halide perovskite devices, revealing complex relationships between morphology and efficiency.

Contribution

The paper introduces an analytical model and statistical simulations to understand the impact of phase segregation patterns and interface states on device performance.

Findings

Increased phase segregation can unexpectedly improve efficiency.

Non-radiative recombination at interfaces degrades device performance.

Critical interface parameters determine system-level variability.

Abstract

Phase segregation is a critical phenomenon that influences the stability and performance of mixed halide perovskite based opto-electronic devices. In addition to the underlying physical mechanisms, the spatial pattern and randomness associated with the nanoscale morphology of phase segregation significantly influence performance degradation a topic which, along with the multitude of parameter combinations, has remained too complex to address so far. Given this, with MAPbI1.5Br1.5 as a model system, here we address the influence of critical factors like the spatial randomness of phase segregation, influence of ion migration, and the effect of increased non radiative recombination at material interfaces. Interestingly, our analytical model and detailed statistical simulations indicate a unique trend morphology evolution with increased phase segregation results, surprisingly, in a recovery in efficiency while non-radiative recombination at grain/domain boundaries results in efficiency degradation. Further, our quantitative and predictive estimates identify critical parameters for interface states beyond which device variability could be an important system level bottleneck. Indeed, these estimates are broadly applicable to systems which undergo phase segregation and have interesting implications to perovskite based optoelectronic devices from stability concerns to engineering approaches that attempt to arrest phase segregation.