Disappearance of rapid photoresponse in ultraviolet illumination of Ag–Sb–S films

Abstract

The photoconduction in Ag0.5Sb0.5S films changes anomalously with the excitation energy. Although the usual instantaneous generation and recombination of photocarriers appear in the resistance of the films for the illumination at a wavelength of 633 nm, the photoresponse becomes slow with time scales of minutes when the illumination is performed at a wavelength of 280 nm. The rapid and slow phototransients are mixed for an intermediate excitation wavelength of 375 nm. In the simultaneous photoexcitation at multiple wavelengths, the response is complex instead of a superposition of the rapid and slow behaviors, indicating the mutual interaction in the photocarrier transport. The ultraviolet (UV) illumination can thereby block the rapid response that should be caused by the visible light. Moreover, the resistance can even increase during the illumination. Although the adsorption of molecules at the film surface plays an important role for the resistance, the anomalous properties are unaffected by the surface condition. They are thus suggested to be the bulk properties of the films, plausibly caused by the defects generated in the UV irradiation.