Bandgap engineering and photodetector applications in Bi(I_1-xBr_x)₃ single crystals

Exploration of low-dimensional semiconductors with tunable band structures is of particular interest in the applications of nano-electronics and optoelectronics. In this work, Bi(I_1−xBr_x)₃ single crystals have been synthesized by a flux-improved physical vapor transport method, where the electronic bandgaps of these single crystals are effectively modulated by the concentration of the halide elements ratios. The first-principle calculations confirm the modulation of bandgap and reveal the orbit contributions for the conduction band minimum and valence band maximum. The properties of Bi(I_1-xBr_x)₃-based photodetectors are measured, where a competition mechanism is identified, leading to the realization of best performance sample with a Br content of 0.18. Our results provide a route to improve the performance of BiI₃-based photodetectors and to achieve controllable response spectra.