A Photoelectrochemical Solar Cell Consisting of a Cadmium Sulfide Photoanode and a Ruthenium-2,2′-Bipyridine Redox Shuttle in a Non-aqueous Electrolyte

A photoelectrochemical (PEC) cell consisting of an n-type CdS single-crystal electrode and a Pt counter electrode with the ruthenium-2,2′-bipyridine complex [Ru(bpy)₃]^2+/3+ as the redox shuttle in a non-aqueous electrolyte was studied to obtain a higher open-circuit voltage (V_OC) than the onset voltage for water splitting. A V_OC of 1.48 V and a short-circuit current (I_SC) of 3.88 mA cm^-2 were obtained under irradiation by a 300 W Xe lamp with 420-800 nm visible light. This relatively high voltage was presumably due to the difference between the Fermi level of photo-irradiated n-type CdS and the redox potential of the Ru complex at the Pt electrode. The smooth redox reaction of the Ru complex with one-electron transfer was thought to have contributed to the high V_OC and I_SC. The obtained V_OC was more than the onset voltage of water electrolysis for hydrogen and oxygen generation, suggesting prospects for application in water electrolysis.