Neumann, B.; Bogdanoff, P.; Tributsch, H.: TiO2-Protected Photoelectrochemical Tandem Cu(In,Ga)Se2 Thin Film Membrane for Light-Induced Water Splitting and Hydrogen Evolution. The Journal of Physical Chemistry C 113 (2009), p. 20980-20989
10.1021/jp903630k
Abstract:
A flexible, thin film Cu(In,Ga)Se2 solar cell deposited on a titanium foil was combined with a TiO2 photocatalyst layer and modified by a niobium-doped titanium oxide front electrode to function as a photoelectrochemical tandem cell/membrane for a direct light-driven hydrogen evolution from aqueous solution. The P680/P700 tandem system in the plant photosynthetic unit is successfully imitated by the concerted and constructive interaction of both semiconductors. Under illumination with UV/vis light, the monolithic TiO2/Ti/Cu(In,Ga)Se2/ CdS/Nb0.03Ti0.97O1.84 tandem membranes produced up to 0.052 μL of hydrogen s-1 cm-2. The hydrogen formation rate is about 7250 μmol h-1 g-1, relative to the amount of TiO2 used. In the long term a significant cost reduction of solar hydrogen evolution will be possible within this system, due to the reduction of solar cell encapsulation costs, the absence of a grid connection between several solar cell modules, and the omission of typical solar cell module equipment, such as a converter and a bypass diode. In addition, no expensive rare-metal-based electrolyzer stack is necessary for hydrogen evolution. The layered structure of the membrane allows an easy substitution and variation of single components, an important criterion for further research and tests with photooxidatively active materials that were not solely limited to the solar UV light fraction, like TiO2 is. Typical electronic and electrochemical requirements of such substitutions are discussed within this paper. Furthermore, the proposed incorporation of the TiO2/Ti/Cu(In,Ga)Se2/CdS/Nb0.03Ti0.97O1.84 tandem membrane into an optical Winston collector system shows that a combined light and thermal solar energy conversion into hydrogen and heat is in principle possible.