Controlled Synthesis of 2D Palladium Diselenide for Sensitive Photodetector Applications

Palladium diselenide (PdSe₂), a thus far scarcely studied group-10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer-scale and homogeneous 2D PdSe₂ film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe₂ with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe₂ exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe₂ layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W⁻¹) and specific detectivity (≈10¹³ Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the as-selenized PdSe₂ is a promising material for optoelectronic application.