Oxide photocathode stacks through facile aqueous solution-gel routes, doping and HTL
Bjorn Joos a b c, Ken Elen a b c, Marlies K. Van Bael a b c, An Hardy a b c
a Hasselt University, Institute for Materials Research (imo-imomec), DESINe, Agoralaan Building D, B-3590 Diepenbeek, Belgium
b Imec, division Imomec, Agoralaan Building D, B-3590 Diepenbeek, Belgium
c EnergyVille, Thor Park 8320, 3600 Genk, Belgium
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#Adinos - Advances in inorganic thin film semiconductors for solar energy conversion: From photovoltaics to solar fuels
València, Spain, 2023 March 6th - 10th
Organizer: Sudhanshu Shukla
Poster, Bjorn Joos, 328
Publication date: 22nd December 2022

Although solar energy is the cleanest and most abundant energy source available on the planet, its use thereof is hindered by its intermittent nature. The ability to harness and conserve solar energy is of utmost importance to guarantee a continuous supply in order to satisfy our energy demands. Artificial photosynthesis is a promising and upcoming technology to store the captured solar energy into energy-dense chemicals such as hydrogen or methanol.[1] Such a solar-energy-to-chemical-energy conversion could be achieved at high efficiency through the use of photo-electrochemical devices. Herein, via the absorption of solar photons, semiconducting photocathodes or photoanodes (or a combination thereof) generate electrons and holes, that are capable to reduce water to hydrogen gas (H2) or to oxidize water to oxygen gas (O2) respectively. Copper-based p-type semiconductors (Cu2O, CuBi2O4, CIGS, CZTS, etc.) take a prominent role as a photocathode due to their abundance, high theoretical photocurrents, and tunable bandgaps (1.0 to 3.5 eV).[1][2]

First, we prepared thin-film phase-pure spinel-type mixed copper bismuth oxide CuBi2O4 through a facile aqueous-solution gel route.[3] Unfortunately, the performance of CuBi2O4 is held back by weak absorption and its low charge carrier diffusion. Hence, every photo-generated exciton counts for the performance of a practical cell. Therefore, the excellent control of the aqueous solution-gel route over elemental stoichiometry was put to use to generate an internal electric field by means of self-doping and to enhance the charge-carrier separation.[4] Copper- and bismuth-containing aqueous precursors of various Cu/Bi compositions were deposited on FTO/glass substrates to generate an electric field gradient. Additionally, doped nicked oxide was developed also by means of the aqueous solution-gel route and used as a hole transfer layer (HTL) between the substrate and the CuBi2O4 absorber. Phase-formation was confirmed by X-ray diffraction and Raman spectroscopy. Photo-electrochemical measurements indicate an enhanced photocurrent of up to 30% by means of the added NiO HTL.

Financial support by Catalisti moonschot project SYN-CAT is acknowledged. SYN-CAT is a cSBO in MOT3 Electrification & Radical Process Transformation.

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