Fig. 3: Series photocathode-photoanode unassisted water-splitting performance.

a Schematic representation of the unassisted PEC water-splitting system using halide perovskite PECs. b Co-plotted photocathode and photoanode polarization curves from most efficient devices showing a maximum theoretical operating current density of 22.7 mA/cm2. c 2-electrode unassisted water-splitting stability test showing degradation after 5 h. d Electrocatalyst-only electrolyzer stability at 20 mA/cm2. e Distribution of STH efficiency across five devices, with an average STH of 12.4 ± 0.7%.