Beyond lead: Progress in stable and non-toxic lower-dimensional perovskites for high-performance photodetection

Photodetectors (PDs) are virtually the key elements of almost every electronic device and are in demand in many fields, namely, fluorescence imaging, machine vision, artificial intelligence, fire and gas monitoring, etc. To detect the incident photons, PDs primarily rely on semiconducting material. Therefore, numerous semiconductor materials including silicon, III-V compounds, carbon nanotubes, and quantum dots have been exploited in PDs for efficient photodetection. However, the high cost of these materials, sophisticated fabrication techniques, and complex processes hinder their commercialization. Recently organo-lead halide perovskites (PVKs) showed their potential in various optoelectronic devices including PDs owing to their exceptional optoelectronic properties, low cost, and facile solution processibility at lower temperatures. Nonetheless, conventional PVKs not only suffer from environmental instability but also rely on toxic lead (Pb), as the main part of their octahedra necessitating the use of non-toxic alternatives. Accordingly, non-toxic alternatives to Pb have been introduced into the PVK structure and have been utilized in numerous optoelectronic devices, including PDs. Among various Pb-free PVKs, lower-dimensional PVKs have not only replaced the toxic Pb in the structure but also provided extended environmental stability to the PVK compounds. The first part of this review explores various types of PDs and key device parameters, while the second part first discusses the unique characteristics of lowerdimensional PVKs. The next section discusses the progress of PDs based on non-toxic, Pb-free PVKs, with a focus on lower-dimensional variants. Detailed device parameters, performance metrics, and device operational and environmental stability are also tabulated. Finally, the review concludes with a summary and an extensive outlook, addressing challenges and outlining future directions for non-toxic PVK-based PDs.