Knowing the optimal performance of perovskite crystals holds the secret to high efficiency of perovskite solar cells (PSCs). Due to the thorny problems of many grains, grain boundaries, pores and surface defects in polycrystalline perovskite films. Some scholars have begun to turn their research direction to how to improve the characteristics of perovskite crystals from the begining. One of the ideas is to replace polycrystalline perovskite films with single crystal perovskite.

      Joule published a report in November 2022, and a research team composed of Korean scholar Nam-Gyu Park and others proved that exquisite control of the perovskite film formation enables the formation of perovskite polyhedral single crystals with well-defined facets. It is found that facets with variant densities and symmetries of atoms govern the perovskite surface chemical and electronic environment and generate significant effects on the photovoltaic performance. Carrier mobility and photocurrent of the (100) crystal facet are almost comparable with those of the (111) facets, which are much higher than those of the (110) one. With the single-crystal-assembled perovskite thin film, the PSC achieves a quasi-steady-state (QSS) efficiency of 24.64% with improved stability to light. Our work provides a deep understanding of the optoelectronic properties of halide perovskite facets.