© 2018 EPFL
Organic Semiconductors for Solar Fuels Reviewed by LIMNO
Splitting water with sunlight and organic semiconductor devices is emerging as a promising approach for the inexpensive and scalable direct solar-to-fuel production.
In a new Review Article by LIMNO, organic semiconductor based devices for solar water splitting are systematically reviewed. The challenges facing the advance of both photovoltaic‐based electrolysis and photo‐electrochemical cells are highlighted while new directions to consolidate these technologies are proposed.
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 H2 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 <1 mA cm−2, and robustness remains a critical issue. However, recent investigations into the direct organic semiconductor/electrolyte interface have brought important insights into free charge generation, the nature of the semiconductor/catalyst interface, and the stability of organic photoelectrodes. Outlooks toward advancing both approaches are discussed.
source: The Ecole polytechnique fédérale de Lausanne (EPFL)