Chloride Treatments Improve Zinc Telluride Absorbers for Photoelectrochemical Carbon Dioxide Reduction.

Utilizing sunlight for photoelectrochemical carbon dioxide reduction reaction (PEC CO RR) is a carbon-neutral path to valuable liquid fuels. Higher quality photoabsorbers are needed to improve the efficiency of the PEC CO RR process. We show how the optoelectronic properties of sputtered ZnTe absorbers can be improved for this purpose via chloride treatments. MnCl and MgCl heat treatments recrystallize ZnTe absorbers to enlarge grains and improve photoluminescence. These material improvements result in the highest PEC CO RR photocurrent density reported for planar ZnTe and >50% Faradaic efficiency to CO formation with diaryliodonium additive in the solution. These results pave the way to integration of polycrystalline thin-film photoabsorbers in PEC CO RR systems.