Organic Semiconductor Based Devices for Solar Water Splitting

Solution processable organic semiconductors are well-established as high-performance materials for inexpensive and scalable solar energy conversion in organic photovoltaic (OPV) devices, but their promise in the economic conversion of solar energy into chemical energy (solar fuels) has only recently been recognized. Herein, the main approaches employing organic semiconductor-based devices toward solar H-2 generation via water splitting are compared and performance demonstrations are reviewed. OPV-biased water electrolysis is seen to advance significantly with the development of the tandem OPV device and the optimization of operating potential and redox catalysts. This approach now exceeds 6% solar-to-hydrogen conversion efficiency while over 10% is reasonably feasible. By contrast, while the direct water splitting by an organic semiconductor in a photo-electrochemical cell has attractive advantages, increasing the performance remains a challenge. Photocathodes employing a bulk-heterojunction have been optimized to give 7-8 mA cm(-2) water reduction photocurrent under standard conditions, but photoanodes remain