All solution-processed SnO2/1D-CsAg2I3 heterojunction for high-sensitivity self-powered visible-blind UV photodetector

Low-dimensional lead-free metal halides have shown considerable potential for visible-blind ultraviolet (UV) photodetectors (PDs) owing to their extraordinary optoelectronic properties. Herein, a high-quality perovskite-like CsAg2I3 thin film was successfully fabricated via the pyridine additive-assisted one-step solution method, and it exhibited an intrinsic p-type behavior and possessed a low exciton binding energy of 202 meV, which was even comparable to low-dimensional lead halide perovskite counterpart and thus favored the separation of photogenerated carriers. Additionally, a type-II n-p heterojunction of SnO2/CsAg2I3 for a self-powered UV PD was configured and investigated experimentally and theoretically. A 4.13-eV-wide-bandgap SnO2 with an extremely low Urbach energy of 0.214 eV was obtained to suppress the persistent photoconductivity effect. The resulting device exhibited pronounced sensitivity with an ultrafast response time of 47/74 µs, which is outstanding among visible-blind UV PDs and two orders of magnitude lower than previously reported CsAg2I3-based UV PDs. The responsivity and detectivity were as high as 0.032 AW−1 and 1.2 × 1011 Jones, respectively. Furthermore, the highly transparent (> 90%) heterojunction for visible light illustrated the superior visible-blind characteristics. The remarkable device performance, solution-processability, and long-term stability reveal a promising strategy for the design of commercial UV PDs that are visible-blind, self-powered, stable, and nontoxic.