Defect-Mediated Slow Carrier Recombination and Broad Photoluminescence in Non-Metal-Doped ZnIn<sub>2</sub>S<sub>4</sub> Nanosheets for Enhanced Photocatalytic Activity
Tanmay Goswami, Dharmendra Kumar Yadav, Himanshu Bhatt, Gurpreet Kaur, Ayushi Shukla, K. Justice Babu, Hirendra N. Ghosh
Abstract
Elemental doping has already been established to be one of the most effective approaches for band-gap engineering and controlled material response for improved photocatalytic activity. Herein atomically thin ZnIn2S4 (ZIS) nanosheets were doped with O and N separately, and the effects of doping were spectroscopically investigated for photocatalytic H2 evolution. Steady-state photoluminescence studies revealed an enhanced charge-carrier population in the doped systems along with a defect-state-induced broad peak in the red region of the spectra. Transient absorption (TA) spectroscopy demonstrated that the conduction-band-edge electrons are transferred on an ultrafast time scale to the inter-band-gap defect states. TA analysis suggests that O and N doping contributes to the defect state concentration and ensures an enhanced photocatalytic activity of the system. This detailed spectroscopic analysis uncovers the role of inter-band-gap defect states in the photocatalytic activity of ZIS and will open new avenues for the construction of nanosheet-based optical devices.