(a) Current versus source–drain bias under different UV light irradiation power. (b) Dependence of photovoltage on irradiated light power density in this work, along with results reported in Refs. [2] and [16]. (c) Extracted photocurrent and responsivity as a function of incident light power. (d) Photocurrent responses at zero bias under on/off (yellow/green time scales) switching of UV light with powers of 1, 3, 5, and 10 mW (from bottom to top).