Nanoscale Chemical Heterogeneity Dominates the Optoelectronic Response over Local Electronic Disorder and Strain in Alloyed Perovskite Solar Cells

TL;DR

This study reveals that nanoscale chemical heterogeneity, rather than electronic disorder or strain, primarily governs the optoelectronic performance of alloyed perovskite solar cells, explaining their high efficiency despite inherent heterogeneity.

Contribution

The paper introduces a new multimodal microscopy approach to visualize and quantify nanoscale chemical, structural, and optoelectronic heterogeneity in perovskite devices, highlighting the dominance of compositional disorder.

Findings

Compositional disorder dominates optoelectronic response.

Nanoscale strain variations have a weak influence.

Chemical gradients enhance defect tolerance.

Abstract

Halide perovskites perform remarkably in optoelectronic devices including tandem photovoltaics. However, this exceptional performance is striking given that perovskites exhibit deep charge carrier traps and spatial compositional and structural heterogeneity, all of which should be detrimental to performance. Here, we resolve this long-standing paradox by providing a global visualisation of the nanoscale chemical, structural and optoelectronic landscape in halide perovskite devices, made possible through the development of a new suite of correlative, multimodal microscopy measurements combining quantitative optical spectroscopic techniques and synchrotron nanoprobe measurements. We show that compositional disorder dominates the optoelectronic response, while nanoscale strain variations even of large magnitude (~1 %) have only a weak influence. Nanoscale compositional gradients drive carrier funneling onto local regions associated with low electronic disorder, drawing carrier recombination away from trap clusters associated with electronic disorder and leading to high local photoluminescence quantum efficiency. These measurements reveal a global picture of the competitive nanoscale landscape, which endows enhanced defect tolerance in devices through spatial chemical disorder that outcompetes both electronic and structural disorder.