Extended Photoresponse in the UV–Visible Region with Multilayered Band Alignment in a In₂S₃-WO₃-ZnO Nanostructure Heterojunction for Photoelectrochemical Water Splitting

The primary purpose of this research is to use a multilayer structure made up of 2D layers of thin film materials with acceptable band alignments for enhanced photoresponse over a wider wavelength range of 300–700 nm. To achieve this, in the present study, a thin layer of WO 3 is deposited in In 2 S 3 -ZnO. Two steps construct the In 2 S 3 -WO 3 -ZnO nanostructure heterojunction: the RF sputtering process to deposit ZnO and WO 3 and the chemical vapor deposition to deposit In 2 S 3 nanoflakes. The continuous hexagonal morphology of the heterojunction shows the highest photocurrent density in the milliampere range. The combined effect of charge carrier separation at the interface and the higher absorption in the entire UV–visible spectral range is responsible for the highest values of performance parameters such as a responsivity value of 440 mA/W, specific detectivity value of 1.0 × 10 10 Jones, and external quantum efficiency value of 80%. The In 2 S 3 -WO 3 -ZnO heterojunction shows small internal resistance to charge carriers, leading to the highest photocurrent density with less recombination of charge carriers. This is the best way to enhance the photoresponse across the complete UV–visible spectral range.