Nanometer-Thick SnP ₂ Se ₆ Flakes for Photodetector Applications

Tin phosphorus selenide (SnP 2 Se 6 ), 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 SnP 2 Se 6 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 SnP 2 Se 6 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 SnP 2 Se 6 as a stable, tunable, and multifunctional two-dimensional semiconductor for broadband optoelectronic applications.