Designing CdS/Se heterojunction as high-performance self-powered UV-visible broadband photodetector

A Se nanorod film is successfully synthesized on a hydrothermally grown CdS layer through a facile vapor phase deposition process, forming a n-CdS/p-Se heterojunction. By virtue of the narrow direct bandgap and large absorption coefficient in UV-visible range of CdS and Se, the integrated CdS/Se photodetector exhibits excellent self-powered behavior in a wide spectral range. In particular, the heterojunction device shows a high photoresponse under weak light irradiation (500 nm, 1.08 μW/cm2) with a large on-off ratio (9 × 103), high responsivity (40 mA/W) and detectivity (1.3 × 1013 Jones), and fast response speed (rise time 2 μs and decay time 22 ms).