Ag2BiI5 perovskite thin films: Studies on structure, morphology, composition and optoelectronic properties for visible photodetector application

Abstract Solution-processed lead halide perovskites have gained considerable attention for the last few years and intense research is going on to find a suitable replacement for lead to reduce the effects of its toxicity, poor stability in ambient conditions, and negative impact on the environment. Herein, we present the synthesis of silver bismuth iodide (SBI) thin films by spin coating of silver iodide and bismuth iodide dissolved in N, N-dimethyl formamide followed by annealing in vacuum. We investigated the effect of bismuth iodide concentration on the SBI perovskite crystal structure and properties. X-ray diffraction analysis revealed the Ag2BiI5 phase with a hexagonal crystal structure. Vibrational spectral analysis by Raman spectroscopy for SBI thin films is reported for the first time. Detailed analysis of the composition and chemical states of the SBI thin films are also described. The Ag2BiI5 perovskites possess a band gap of 1.71 eV which makes them useful for optoelectronic applications. Morphology, optical and electrical properties of the perovskites are influenced by the bismuth iodide concentration. Here, we developed a highly sensitive and reproducible silver bismuth pentaiodide (Ag2BiI5) based visible light detector. The detector showed good responsivity, sensitivity as well as an incident light intensity-dependent behavior when illuminated with 532 nm laser suggesting them as a suitable candidate for various optoelectronic applications.