Emerging Opportunities in Lead-Free and Lead–Tin Perovskites for Environmentally Viable Photodetector Applications

In modern society, photodetectors (PDs) have permeated virtually all areas of human life, from home appliances to space exploration. This versatility generates a high demand for photodetectors. It is attributed to their ability to detect signals spanning a broad spectrum of wavelengths while possessing advantageous mechanical properties such as light weight, flexibility, and low cost. Metal halide perovskites (PSKs) have recently emerged as effective photodetectors because their detection range extends from the visible spectrum to the near-infrared (NIR) spectrum through the adjustment of the chemical composition. In addition to having notable successes in photovoltaic applications, perovskites have gained attention in photodetector applications due to their superior optoelectronic properties. Incorporating toxic Pb offsets the desirability of such a high performance as the main component of perovskites. This issue was addressed by replacing Pb with relatively nontoxic Sn to retain the unique optoelectronic properties of perovskites. To promote the continued advancement of perovskites with reduced toxicity, we provide a comprehensive overview of current research on Sn and Sn–Pb mixed perovskites, emphasizing crystal structures, optoelectronic properties, synthesis, and modification methods. We then highlight exemplary applications of Sn and Sn–Pb perovskites through detailed introductions. Simultaneously, current challenges and respective solutions to the development of Sn perovskites are discussed in this Review. This Review concludes with a novel outlook on future research directions for Sn-rich perovskite photodetectors as potential candidates for enhancing light signal detection technologies. We explain how this enhancement enables performance comparable to that of commercially available crystalline Si and III–V photodetectors.