Anisotropy in Perovskite Single Crystals: From Fundamentals to Applications

Single crystals of semiconductor materials have been extensively studied in optoelectronic applications because of the absence of grain boundary, lesser defects, and long-range order of crystallinity. Due to their multifaceted character, crystals are very often found to have significant anisotropic properties. These anisotropic properties lead to a considerable variation in their fundamental properties and optoelectronics applications. In the past decade, halide perovskites have emerged as one of the most exciting classes of semiconductors due to their rich photophysical properties leading to applications in solar cells, light-emitting diodes, photodetectors, etc. Especially, perovskite single crystals (PSCs) with an absence of grain boundaries, remarkably longer carrier diffusion lengths, significantly lower trap densities, and long-range order have received wide attention in large-scale device deployment. Interestingly, PSCs also exhibit strong anisotropy-dependent fundamental properties, and correspondingly their device applications are highly tunable. Here, in this feature article, we address a molecular perspective focusing on the structural, optical, and electronic anisotropy in PSCs. In addition, we discuss how anisotropy can affect the performance of PSCs-based devices. Furthermore, we highlight the future directions for implementing a fundamental understanding of the anisotropic response of PSCs to design novel and emergent optoelectronics devices.