All Solution-Processed, Hybrid Organic-Inorganic Photocathode for Hydrogen Evolution.

Nowadays, the efficient, stable, and scalable conversion of solar energy into chemical fuels represents a great scientific, economic, and ethical challenge. Amongst the available candidate technologies, photoelectrochemical water-splitting potentially has the most promising technoeconomic trade-off between cost and efficiency. However, research on semiconductors and photoelectrode architectures suitable for H evolution has focused mainly on the use of fabrication techniques and inorganic materials that are not easily scalable. Here, we report for the first time an all solution-processed approach for the fabrication of hybrid organic/inorganic photocathodes based on organic semiconductor bulk heterojunctions that exhibit promising photoelectrochemical performance. The sequential deposition of inorganic material, charge-selective contacts, visible-light sensitive organic polymers, and earth-abundant, nonprecious catalyst by spin coating leads to state-of-the-art photoelectrochemical parameters, comprising a high onset potential [+0.602 V vs reversible hydrogen electrode (RHE)] and a positive maximum power point (+0.222 V vs RHE), a photocurrent density as high as 5.25 mA/cm at 0 V versus RHE, an incident photon-to-current conversion efficiency at 0 V versus RHE of above 35%, and 100% faradaic efficiency for hydrogen production. The demonstrated all solution-processed hybrid photoelectrodes represent an eligible candidate for the scalable and low-cost solar-to-H conversion technology that embodies the feasibility requirements for large area, plant-scale applications.