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The power conversion efficiency of tandem dye-sensitized photoelectrosynthesis cells is limited by the number of p-type metal oxide semiconductors and chromophores available for the photocathode. Here, a new class of donor–acceptor–donor organic chromophores is introduced with deep highest occupied molecular orbital (HOMO) levels to target hole injection into PbTiO3, a wide-band-gap metal oxide alternative to NiO. Electrochemical measurements show that the range of the chromophores’ electron affinity can be tuned between ∼4.30 and 3.30 eV and the ionization potential can be kept at ∼−6.50 eV. The absorption profiles for these chromophores span throughout the visible region. The new chromophore reported here, benzobis(thiadiazole)bis(thiophene-3-carboxylic acid), T2-BBT, adsorbed onto PbTiO3, obtained a maximum absorbed photon-to-current conversion efficiency of 54%. These results highlight the importance of designing chromophores with favorable redox potentials to study promising p-type wide-band-gap metal oxides for photocathodic applications.

Nhon, L.; Taggart, A. D.; Moot, T.; Brennaman, M. K.; Jagadesan, P.; Schanze, K. S.; Cahoon, J. F.; Reynolds, J. R. Organic Chromophores Designed for Hole Injection into Wide-Band-Gap Metal Oxides for Solar Fuel Applications. Chem. Mater. 2020, 32 (19), 8158-8168.

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