Highly Enhanced Performance and Temperature-Invariant Robust Blue-UV Photosensing in Quasi-2D van-der-Waals TlGaS2 Exfoliated Microflake.

To date, transition metal dichalcogenides (TMDCs) are mostly explored as 2D semiconducting materials due to their distinctive properties as compared to their bulk counterparts while similar research focus on post-transition metal dichalcogenides (PTMDCs) is still in infancy. Here, we demonstrate an interesting contrast between photocarrier dynamics in quasi-2D van der Waals TlGaS2, revealed through a comparative study of single-crystal and exfoliated microflake. The single crystal exhibits pronounced temperature-sensitive spectral features indicative of strong carrier-phonon coupling and delivers a maximum responsivity of 5 mA/W under 490 nm illumination. In contrast, the microflake shows faster, weakly temperature-dependent carrier relaxation and narrowband blue-UV selectivity. Remarkably, the microflake demonstrates an enhanced responsivity of 32.1 mA/W, with a negligible response to green and red light, revealing TlGaS2 single crystals as visible photodetectors with optically tunable switching, while the microflake as a low-power, blue-UV selective, temperature-robust optical-digital conversion system. Most importantly, this work provides fundamental insight into temperature-dependent carrier transport and dimensionality-driven photocarrier dynamics in quasi-2D PTMDCs.