Solar Cells Based on Pb-Free and Perovskite-Inspired Materials: Futuristic of Perovskite Solar Cells

The breakthrough in 2012 showed how next-generation solar cells lead to perovskite-based materials and devices. Perovskite solar cells (PSCs) have achieved power conversion efficiency (PCE) ∼26.1% on rigid and ∼25.09% on flexible substrates. The long lifetime of ∼8760 h is reported for PSCs using Pb-based perovskites as an absorber. However, the question of Pb toxicity in PSCs is still a major issue in the commercialization path. The Pb toxicity and poor stability of Pb-related materials hinder their industrial applications. The various efforts from the past decade resulted in the development of tin halide perovskites, defect-structured perovskites, double perovskites, and perovskite-inspired materials such as rudorffites. However, the PCE of these newly developed materials falls short of that of the corresponding Pb-halide-based perovskites. Hence, herein, a review of the present status of Pb-free perovskite materials and related solar cell devices will be discussed. Further, the review will summarize the recent developments in perovskite materials free from lead and useful for solar cells. The Sn-, Ge-, Sb-, and Bi-based perovskite materials and their combinations and double perovskites would be explored for their futuristic use in solar cells. In summary, the latest progress, outstanding challenges, and future directions of Pb-free halide perovskites, thin films, and nanocrystals will also be reviewed. The review will focus on Pb-free materials and optical and optoelectronic properties to give directions to the researchers of today and tomorrow who are working in the field and may join the field shortly.