SEM picture of the Sb2SeTe2 nanosheet. The top-right figure shows the linear current–voltage curve indicating the ohmic contact between the Pt electrodes and Sb2SeTe2 nanosheet.

The photocurrent was performed in the Sb2SeTe2 topological insulator at a wavelength of 532 nm. It exhibits extremely high performance that the responsivity and the photoconductive gain reach 2293 AW−1 and 5344 at 1 V. This high photoresponse is orders of magnitude higher than most reported values in topological insulators and two-dimensional transitional metal dichalcogenides. This finding suggests that the Sb2SeTe2 nanoflake has great potential for future optoelectronic device applications.