Photocathodes beyond NiO: charge transfer dynamics in a π-conjugated polymer functionalized with Ru photosensitizers

• Main Authors: Ruri A. Wahyuono, Bianca Seidler, Sebastian Bold, Andrea Dellith, Jan Dellith, Johannes Ahner, Pascal Wintergerst, Grace Lowe, Martin D. Hager, Maria Wächtler, Carsten Streb, Ulrich S. Schubert, Sven Rau, Benjamin Dietzek
• Format: Article
• Language: English
• Published: Nature Publishing Group 2021-02-01
• Series: Scientific Reports
• Online Access: https://doi.org/10.1038/s41598-021-82395-x
• ISSN: 2045-2322

Abstract A conductive polymer (poly(p-phenylenevinylene), PPV) was covalently modified with RuII complexes to develop an all-polymer photocathode as a conceptual alternative to dye-sensitized NiO, which is the current state-of-the-art photocathode in solar fuels research. Photocathodes require efficient light-induced charge-transfer processes and we investigated these processes within our photocathodes using spectroscopic and spectro-electrochemical techniques. Ultrafast hole-injection dynamics in the polymer were investigated by transient absorption spectroscopy and charge transfer at the electrode–electrolyte interface was examined with chopped-light chronoamperometry. Light-induced hole injection from the photosensitizers into the PPV backbone was observed within 10 ps and the resulting charge-separated state (CSS) recombined within ~ 5 ns. This is comparable to CSS lifetimes of conventional NiO-photocathodes. Chopped-light chronoamperometry indicates enhanced charge-transfer at the electrode–electrolyte interface upon sensitization of the PPV with the RuII complexes and p-type behavior of the photocathode. The results presented here show that the polymer backbone behaves like classical molecularly sensitized NiO photocathodes and operates as a hole accepting semiconductor. This in turn demonstrates the feasibility of all-polymer photocathodes for application in solar energy conversion.