Pure Organic Semiconductor-Based Photoelectrodes for Water Splitting

Currently, photoelectrochemical water-splitting research is dominated by inorganic and organic–inorganic hybrid photoelectrodes. Although organic semiconductors have several advantages over their inorganic counterparts, the development of photoelectrodes based on pure organic materials has been lagging for the last decade. Recent improvements in molecular design, synthesis, and processing of organic semiconductors, such as polythiophenes, graphitic carbon nitrides, conjugated acetylenic polymers, alternating donor–acceptor-conjugated polymers, and N-containing fused-ring small molecules, significantly enhance the performance of these photolectrodes without added cocatalysts. Although this research has been conducted over the past few years, this overlooked topic still stays unexplored, with more efficient materials yet to be discovered. Herein, the early development and recent advances of exclusively organic photoelectrodes for water splitting are summarized and brief perspectives for future improvements are provided.