Efficient photoelectrochemical nanoemitter solar cell

Photoelectrochemical solar cells convert solar energy into electricity as fuels. The operation is based on the contact potential between a semiconductor and a redox electrolyte that results in the separation of photoinduced excess charge carriers. The applicability of photoelectrochemical solar energy conversion, however, is limited by photocorrosion at the reactive interface. Here, a new efficient photoelectrochemical solar cell is reported that avoids contact between semiconductor and electrolyte. The operational principle is based on metallic nanoemitters that form local contacts between the semiconductor absorber and the redox electrolyte while the remaining semiconductor surface is covered by an insulating anodic oxide. The nanoporous oxide, prepared by an oscillatory self-organised electrochemical process, serves as a template for spatially selective metal nanoemitter electrodeposition, resulting in a Si/SiO2/Pt nanocomposite structure after Pt deposition. In contact with I-/I-3(-) redox electrolyte, a solar conversion efficiency of 11.2% has been obtained with the cell n-Si/SiO2/Pt/I-/I-3(-)/C. The novel concept is characterized by the scalability of the employed oscillatory process, low-temperature processing, protection of the semiconductor surface from the solution and applicability in monolithically integrated solar fuel generating devices (photoelectrocatalysis) and solid-state solar cells. (C) 2008 Elsevier B.V. All rights reserved.