Recent progress of lead-free halide double perovskites for green energy and other applications

In recent years, the metal halide perovskites (MHPs) have gained substantial interest due to their versatile applications in the field of the solar cell, Field-Effect Transistor (FET), and Light-Emitting Diode (LED), sensor, photocatalyst, etc. However, instability and toxicity are two major issues hindering their large-scale commercialization. In this regard, the growth of lead-free halide double perovskites is crucial to solving the above issues. The lead-free halide double perovskites have versatile applications as photovoltaic, thermoelectric, spintronic, LED, and photocatalytic materials. This article discussed both theoretical and experimental assessments of the optical, electronic, magnetic, and thermoelectric properties of lead-free halide double perovskites. In addition, we have discussed their structural, mechanical, and thermal stabilities of lead-free halide double perovskites with the help of experimental and theoretical data. Furthermore, we have highlighted the up-to-date progress of lead-free halide double perovskites for applications in the field of photovoltaic, field-effect transistor (FET), and light-emitting diode (LED), photocatalyst, thermoelectric, spintronic, and memristors. Finally, challenges and future outlooks for using these materials for said applications are discussed.