Orientation-Related Giant Photothermoelectric Energy Conversion in Quasi-One-Dimensional van der Waals TaSe Crystals.

Featuring the capabilities of self-power, low dark current, and broadband response, photothermoelectric (PTE) detection demonstrates great potential for application in the military and civilian fields. The development of materials with an intrinsically high efficiency for PTE energy conversion and the in-depth study of its thermoelectric properties on the device performance are of great significance. Here, we reported a quasi-one-dimensional (quasi-1D) van der Waals (vdW) TaSe crystal as a promising material candidate for PTE detection. Benefiting from the 1D confined effect for photon and electron transport, the TaSe nanoribbon crystallized along the atomic chain direction demonstrates a size-dependent thermal conductivity and Seebeck coefficient. With the nanoribbon width downscaled from 5.7 μm to 200 nm, the resulting PTE detector reveals a pronouncedly enhanced photoresponsivity by more than 1 order of magnitude, demonstrating an extremely high value of 33 V/W among the best state-of-the-art PTE devices. More importantly, the anisotropic electrical, thermal, and thermoelectric properties in the TaSe crystal contribute to the orientation-related PTE energy conversion, yielding an anisotropic ratio of photoresponsivity as large as 2.5 under 532 nm light illumination. Our study provides experimental evidence of orientation-related giant PTE photodetection in the quasi-1D vdW TaSe crystal, which provides possibilities for the development of future optoelectronic devices.