Phase segregation induced efficiency degradation and variability in mixed halide perovskite solar cells

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 MAPbI(1.5)Br(1.5) as a model system, here we address the influence of critical factors like the spatial randomness of phase segregation, the influence of ion migration, and the effect of increased non-radiative recombination at domains/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 domains/ 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 that undergo phase segregation and have interesting implications to perovskite-based optoelectronic devices fromstability concerns to engineering approaches that attempt to arrest phase segregation. Published under an exclusive license by AIP Publishing.