Dye-Sensitized Solar Hydrogen Production: The Emerging Role of Metal-Free Organic Sensitizers

The production of hydrogen from sunlight and water is finding an increasingly important role in the production of clean fuels from sustainable and abundant energy sources. In this process, commonly referred to as artificial photosynthesis, the role of the dye sensitizer is critical for optimizing the harvesting of visible light and triggering the reduction reaction at the catalytic active site. In recent decades organometallic sensitizers have mainly been studied, often requiring the use of scarce and, in some cases, toxic elements. This microreview describes the state of the art in the use of metal-free organic sensitizers, highlighting advantages over their organometallic counterparts. The main design and synthetic strategies, specific properties, and device performances are presented. Thanks to recent advances and lower manufacturing costs, organic sensitizers seem set to be of increasing importance for next-generation clean fuels.