AbstractMetal halide perovskite materials have excellent photoelectric properties, including high absorption coefficient, long charge carrier diffusion length, and low exciton binding energy, making them excellent candidates for photoconversion devices. In the past decade, great progress has been made in improving the performance of perovskite‐based solar cells and photodetectors. However, perovskite devices need to be endowed with more functionality to meet practical application requirements. In this regard, the three major trends in perovskite device development involving flexibility, transparency, and self‐healing have attracted wide interests. This review first summarizes the fundamental design principles of endowing perovskite devices with more functionality. Specifically, the functionalization is realized through elaborate substrate and electrode selection, perovskite layer modification, and device layout. This review presents the recent advances and specific requirements for functionalization of perovskite devices according to the three basic components: substrate, electrode, and perovskite layer. Finally, potential challenges and future research directions in this field are outlined. The aim of this review is not only to shed light on the basic design principles of functionalized perovskite devices, but also to serve as the roadmap for future exploration in perovskite devices.