Hybrid organic-inorganic H2-evolving photocathodes: understanding the route towards high performances organic photoelectrochemical water splitting.

A promising, yet challenging, route towards renewable production of hydrogen is the direct conversion of solar energy at a simple and low cost semiconductor/water junction. Despite the theoretical simplicity of such a photoelectrochemical device, different limitations among candidate semiconductor materials have hindered its development. After many decades of research on inorganic semiconductors, a conclusive solution still appears out of reach. Here, we report an efficient hybrid organic-inorganic H-2 evolving photocathode, consisting of a donor/acceptor blend sandwiched between charge-selective layers and a thin electrocatalyst layer. The role and stability of the different interfaces are investigated, and the conductive polymer is proven to be an efficient material for a semiconductor/liquid PEC junction. The best performing electrodes show high performances with a photocurrent of 3 mA cm(-2) at 0 V vs. RHE, optimal process stability with 100% faradaic efficiency during electrode's lifetime, excellent energetics with +0.67 V vs. RHE onset potential, promising operational activity of several hours and by-design compatibility for implementation in a tandem architecture. This work demonstrates organic semiconductors as a radically new option for efficient direct conversion of solar energy into fuels, and points out the route towards high performance organic photoelectrochemical water splitting.