**Abstract**

Organic–inorganic hybrid perovskites, which combine the superior optical and electronic properties and solution-processed manufacturing, have emerged as a new class of revolutionary optoelectronic devices with the potential for various practical applications. Encouraged by the advantages of longer carrier diffusion length, higher carrier mobility and lower trap densities as compared to the polycrystalline counterparts', increasing research attention has focused on preparation and optimization of perovskite crystal candidates, via using various facile growth techniques, for the development of a wide range of optoelectronic applications. This chapter presents a comprehensive review of recent advances in the field of optoelectronic technologies based on different forms of single crystals, including bulk crystals and thin ones, with emphasis placed on the optimization of crystals and the relationship among the charge-carrier transport, operation mechanism, device architecture, and device performance. First, we introduce the main methods used to prepare bulk and thin single crystals, and analyze several aspects of their properties. Thereafter, the applications of single crystals into solar cells, photodetectors, light-emitting diodes, and lasers, are discussed in depth. Finally, we summarize the challenges of perovskite single crystals and propose further improvements in the synthesis approaches and device applications.

**Keywords:** hybrid perovskite crystals, optoelectronics, solar cells, photodetectors, LEDs
