Synergistic Effects of Defects and Strain on Photoluminescence in Van der Waals Layered Crystal AgScP2S6

Metal thiophosphates (MTPs) are a large family of 2D materials that exhibit large structural and chemical diversity. They also show promise for applications in energy harvesting and photodetection. Strain and defect engineering have previously been demonstrated as useful mechanisms to tune several properties of MTPs such as resistivity, magnetic state, and electronic band gap. However, the effect of these stimuli on engineering tunable light emission in MTPs remains unexplored. Here, it is experimentally demonstrated that sulfur vacancies in metal thiophosphate ${\mathrm{AgScP}}_2{\mathrm{S}}_6$ allow defect-state-to-valence-band transitions leading to visible light emission at sub-bandgap energies, while structural defects in the material can enhance and modulate the photoluminescence spectrum. It is also showed that the structural-defect-enhanced light emission can be further tuned by temperature-induced strain gradients.