High Gain Solution-Processed Carbon-Free BiSI Chalcohalide Thin Film Photodetectors

Chalcohalide semiconductors are an emergent class of materials for optoelectronics. Here, the first work on BiSI chalcohalide thin film photodetectors (PDs) is presented. An entirely new method for the fabrication of bismuth chalcohalide thin films (BiOI and BiSI) is developed. This method circumvents the use of any ligands or counter ions during fabrication and provides highly pure thin films free of carbon residues and other contaminants. When integrated into lithographically patterned lateral PDs these BiSI thin films show outstanding performances and high stability. The direct approximate to 1.55 eV bandgap of BiSI perfectly accommodates optical sensing over the full visible spectrum. The responsivity (R) of the BiSI PDs reaches 62.1 A W-1, which is the best value reported to date across chalcohalide materials of any type. The BiSI PDs display remarkable sensitivity to low light levels, supporting a broad operational detectivity approximate to 10(12) Jones over four decades in light intensity, with a peak specific detectivity (D*) of 2.01 x 10(13) Jones. The dynamics of photocurrent generation are demonstrated to be dominated by photoconductive gain. These results cement BiSI as an exciting candidate for high performance photodetector applications and encourage ongoing work in BiSX (X = Cl, Br, I) materials for optoelectronics.

Automated summary

Chalcohalide semiconductor materials, particularly bismuth chalcohalide thin films like BiSI, have shown promising performance in optoelectronic applications. A novel fabrication method for bismuth chalcohalide thin films has been developed in this study, resulting in pure films with excellent properties. BiSI thin films integrated into lateral photodetectors exhibited high responsivity, exceptional sensitivity to low light levels, and a peak specific detectivity that is among the best reported for chalcohalide materials. These results highlight BiSI as a strong candidate for high-performance photodetector applications in the field of optoelectronics.