Photocathodes beyond NiO:charge transfer dynamics in a π‑conjugated polymer functionalized with Ruphotosensitizers

Ruri A. Wahyuono (1, 2, 3) , Bianca Seidler (1, 2, 4) , Sébastian Bold (1, 2, 5) , Andrea Dellith (1) , Jan Dellith (1) , Johannes Ahner (6, 7) , Pascal Wintergerst (4) , Grace Lowe (4) , Martin D. Hager (6, 7) , Maria Wächtler (1, 2) , Carsten Streb (4) , Ulrich S. Schubert (6, 7) , Sven Rau (4) , Benjamin Dietzek (1, 2, 7)

1 Department Functional Interfaces, Leibniz Institute of Photonic Technology
2 Institute of Physical Chemistry
3 Department of Engineering Physics, Institut Teknologi Sepuluh
4 Institute of Inorganic Chemistry I.
5 SolHyCat - Solar fuels, hydrogen and catalysis
6 IOMC - Institute of Organic Chemistry and Macromolecular Chemistry [Friedrich Schiller University Jena]
7 Center for Energy and Environmental Chemistry (CEEC Jena)

A conductive polymer (poly(p-phenylenevinylene), PPV) was covalently modified with Ru-II 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 similar to 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 Ru-II 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.

Domaines: Polymères

Ruri A. Wahyuono, Bianca Seidler, Sébastian Bold, Andrea Dellith, Jan Dellith, et al.. Photocathodes beyond NiO:charge transfer dynamics in a π‑conjugated polymer functionalized with Ruphotosensitizers. Scientific Reports, 2021, 11 (1), pp.2787. ⟨10.1038/s41598-021-82395-x⟩. ⟨hal-03178156⟩