Rare‐Earth‐Based Lead‐Free Halide Double Perovskites for Light Emission: Recent Advances and Applications

Abstract The double perovskite material of Cs 2 NaRECl 6 ‐type, utilizing rare‐earth (RE) ions as trivalent element, has attracted widespread interest due to its unique optoelectronic properties and wide range of applications. It displays rich optical properties, including visible and infrared light emission through down‐shifting, as well as up‐conversion emission and radiation‐induced emission. These exceptional optical properties make it a promising material for optoelectronic devices such as detectors, light‐emitting diodes, lasers and energy storage batteries but also show unique advantages in anti‐counterfeiting technology and imaging. In this article, the latest progress is reported and challenges in the crystal structure, material preparation, optoelectronic performance, and various applications of lead‐free halide double perovskite (HLDPs) compounds. This is also outline prospective research directions of existing materials, with the aim of facilitating the discovery of new HLDPs materials.