Figure 4. Investigation of possible mechanisms behind the photocurrent degradation.

(a) J–V characteristics before (blue square–pink line) and after 2 h of constant illumination (red triangles–black line); voltages are scanned from forward to reverse (symbols) and from reverse to forward (lines) with delay time of 3 ms (other scan rates are presented in Supplementary Information and do not show hysteresis). (b) V_OC evolution over several light on (red curves) and light off (space in between) cycles. (c) Control measurement of time evolution of the photocurrent by applying a forward bias when the device is rested in the dark (red circles) in comparison to the constantly illuminated device (black line).