Electrochemical impedance measurements for Sb2Se3 photocathodes: EIS measurements were performed with a BioLogic SP-300. The bias potential steps were approximately 50 mV and the equilibrium time at each bias potential step was 17s. The frequency range used was 7 MHz to 0.1 Hz. For the EIS measurements under illumination, a white light bias by LEDs (SP-12-W5, cool white Luxeon Rebel) was used. Due to the large mismatch of the spectra of the white LEDs and Xenon lamp with AM 1.5G filter, the percentages of the LED light (10 % or 50 % sun) are only approximate. The EIS spectra were fitted with Zview software from Scribner.