Polymer-based photocathodes with a solution-processable cuprous iodide anode layer and a polyethyleneimine protective coating

Organic semiconductors have been proven to be suitable for efficient photovoltaic generation during the last decade but have been scarcely assessed as photoelectrochemical devices. In this work we present the fabrication and characterization of a new efficient hybrid organic/inorganic photocathode for hydrogen evolution showing both a positive onset potential (+0.702 V vs. RHE) and a maximum power point (+0.303 V vs. RHE). We demonstrate that a conventional P3HT:PCBM bulk heterojunction architecture enclosed between a solution-processed cuprous iodide hole selective layer and a Pt-decorated nanostructured TiO2 layer can efficiently photogenerate hydrogen under acidic conditions under simulated 1 Sun illumination. This architecture showed initial photocurrents as high as 8 mA cm−2 at 0 V vs. RHE, IPCE above 50%, 100% faradaic efficiency and an ideal ratiometric power-saved figure of merit equal to 1.21%. Finally, with the addition of a solution-processed polyethyleneimine protective coating, we improved the device stability. This work paves the way to the use of hybrid organic/inorganic photocathodes for efficient solar hydrogen generation.