Nanometer-Thick SnP ₂ Se ₆ Flakes for Photodetector Applications

Tin phosphorus selenide (SnP2Se6), a member of the metal phosphorus trichalcogenide family, is garnering significant interest due to its wide bandgap and promising physical properties for use in stable, broadband optoelectronics. This work investigates SnP2Se6 thin flakes of varying thicknesses, analyzing them with Raman spectroscopy and measuring the spectral responses of fabricated photodetectors. Raman measurements revealed no notable peak shifts as a function of flake thickness, indicating structural stability. However, the SnP2Se6 photodetectors demonstrated a significant redshift in cutoff wavelength─ranging from 640 to 900 nm─as the flake thickness increased. This redshift corresponds to a tunable bandgap of approximately 1.4 to 1.9 eV. A strong positive correlation (Pearson’s R = 0.94) is observed between the number of layers and the redshift in cutoff wavelength. These results confirm the potential of SnP2Se6 as a stable, tunable, and multifunctional two-dimensional semiconductor for broadband optoelectronic applications.