Advances and challenges in understanding the microscopic structure–property–performance relationship in perovskite solar cells

The emergence of perovskite photovoltaic technology is transforming the landscape of solar energy. Its rapid development has been driven by the advances in our understanding of the thin-film microstructures of metal halide perovskites and their intriguing correlations with optoelectronic properties, device efficiency and long-term stability. Here we discuss the morphological characteristics of three key microstructure types encountered in perovskites, which include grain boundaries, intragrain defects and surfaces. To reveal detailed structural information of these microstructure types via tailored characterizations is crucial to probe their detrimental, neutral or beneficial effects on optoelectronic properties. We further elaborate the impacts of these microstructures on the degradation modes of perovskites. Representative examples are also presented, which have translated fundamental understandings to achieve state-of-the-art perovskite solar cells. Finally, we call for more attention in probing hidden microstructures and developing high-spatiotemporal-resolution characterizations, as well as harnessing the potential merits of microstructural imperfections, towards an elevated understanding of microstructure–property–performance relationships for the next solar cell advances.