Solar-blind ultraviolet photodetector derived from direct carrier transition beyond the bandgap of CdPS₃ single crystals

Wide-bandgap semiconductors have demonstrated considerable potential for fabricating solar-blind ultraviolet (SBUV) photodetectors, which are extensively used in both civilian and military applications. Despite this promise, the limited variety of semiconductors with suitable bandgaps hampers the advancement of high-performance SBUV detectors. In this study, we synthesized CdPS₃ transparent single crystals using the chemical vapor transport (CVT) method. Density functional theory (DFT) calculations suggest that the bandgap of CdPS₃ decreases as the material’s thickness increases, a finding corroborated by subsequent absorption spectra and photoelectric response measurements. The as-prepared CdPS₃ nanosheets were employed as channels in photodetectors, demonstrating outstanding photoelectric performance in the solar-blind ultraviolet range (at 254 and 275 nm) with high responsivity (0.3 A/W), high specific detectivity (5.5 × 10⁹ Jones), rapid response speed (2.6 ms/3.4 ms), and exceptionally low dark current (2 pA). It is noteworthy that these nanosheets exhibit almost no sensitivity to 365 nm and visible light irradiation, attributable to the direct carrier transition beyond the broad bandgap in CdPS₃. Furthermore, high-quality imaging was achieved under different gate voltages using 275 nm ultraviolet light, underscoring the potential of CdPS₃ as a new material for high-performance SBUV optoelectronic detection.