Colloidal Quasi‐2D Cs ₂ AgBiBr ₆ Double Perovskite Nanosheets: Synthesis and Application as High‐Performance Photodetectors

ABSTRACT The search for non‐toxic lead‐free halide perovskites that can compete with the lead‐based counterparts has led to the emergence of double perovskites as potential candidates. Among many options, Cs ₂ AgBiBr ₆ stands out as one of the most suitable eco‐friendly materials for numerous optoelectronic applications. In this study, quasi‐2D Cs ₂ AgBiBr ₆ nanosheets (NSs) were prepared via the low‐temperature injection colloidal synthesis and used to fabricate high‐performance photodetectors in a transport‐layer‐free architecture. The reaction temperature and ligands played vital roles in the structural purity, shape, and size of the synthesized Cs ₂ AgBiBr ₆ NSs. The fabricated NSs disclosed lateral sizes of up to 1.4 µm and are only a few nanometers thick. The high‐performance photodetectors fabricated using the Cs ₂ AgBiBr ₆ NSs yielded a high detectivity ( D ) of 1.15 × 10 ¹² Jones, responsivity ( R ) of 121 mA/W, a notable on‐off ratio of 2.39 × 10 ⁴ , and a fast rise and decay time of 857 and 829 µs, respectively. The device demonstrates remarkable stability. Basically, it sustains its entire photocurrent after storage in ambient conditions for 80 days. This work showcases a pathway for the colloidal synthesis of quasi‐2D Cs ₂ AgBiBr ₆ lead‐free double perovskite NSs with suitable properties for high‐performance photodetection and other optoelectronic applications.