Elucidating the regulation mechanism of the photoelectrochemical effect of photocathodes on battery discharge voltages: a case study of aqueous zinc-iodine batteries.

We demonstrated a method to increase the discharge voltages of zinc-iodine batteries by introducing a p-type semiconductor photocathode to trigger the photoelectrochemical reduction reaction of the cathode redox. Accordingly, the photogenerated voltage across the semiconductor/liquid junction interface would be added to the discharge voltages of zinc-iodine batteries, realizing a discharge voltage (1.49 V) exceeding the theoretical value (1.30 V) under illumination, which is equivalent to an energy density increase of 31% compared to that of zinc-iodine batteries under dark conditions.