Halide Double Perovskites

Halide double perovskites (HDPs) have emerged as a promising alternative to traditional, single-metal perovskites (ABX 3 ). Besides offering improved stability and reduced toxicity relative to the widely used lead perovskites, HDPs offer a vast and unexplored chemical space. In addition, the vast compositional diversity of HDPs makes them promising candidates for several applications, such as solar cell absorbers, light-emitting materials, photodetectors, catalysts, and others. In this chapter, we will review the history of HDPs, define what HDPs are, and study their compositional and structural characteristics, properties, and electronic structure. Then, we will discuss some of the known and potential applications of HDPs. We will then focus on to HDP-related families of materials, such as the dimensionally reduced HDPs. Finally, we will offer a perspective on the short-, medium-, and long-term challenges and outlook of this exciting family of materials.