Recent developments of lead-free halide double perovskites: a new superstar in the optoelectronic field

Metal halide perovskites have come to the limelight in the field of optoelectronic devices in the last few decades. Owing to their unique optical and electronic properties along with variable morphologies, perovskite materials have attracted widespread attention compared to conventional semiconductors. The power conversion efficiency of perovskites has reached beyond 25% in the last few years. Besides solar cell application, perovskite materials are explored towards light emitting diodes, sensors, photoconductors and other electrochemical applications. Unfortunately, the toxicity and instability issues render the large-scale commercial application of halide perovskite despite having excellent characteristics with flexibility for optoelectronic applications. The scientific community is searching for lead-free non-toxic and stable perovskites to overcome this problem. Especially double perovskites have gained importance in this purpose due to their similar characteristics to lead halide perovskites. Moreover, double perovskites exhibit interesting optical and morphological properties. In this review we discuss the different aspects of double perovskites in detail.