One way of improving the efficiency of dye-sensitised solar cells is to use two photoelectrodes in a tandem device, one harvesting the high energy photons, and the other harvesting the low energy photons [1]. This enables the photovoltage to be increased, whilst maximizing light harvesting across the solar spectrum. Despite their promise, a tandem cell with a higher efficiency than the state-of-the-art ‘Grätzel’ cell has not yet been achieved. This is because the performances of photocathodes are significantly lower than TiO2-based anodes, and the p-type concept has been largely unexplored since the first device was prepared in 1999 [2]. The small potential difference between the valence band of the NiO, p-type semiconductor, and the redox potential of the electrolyte and the faster charge-recombination reactions compared to the TiO2 system limits the efficiency. In recent years the researchers have made progress by developing new photosensitisers [3]. In parallel the researchers have investigated the charge-transfer processes to determine the mechanism and limitations to efficiency [4]. This has increased our understanding of the redox processes at the dye/electrolyte and NiO/electrolyte interfaces [5]. The fundamental limitation of these devices arises from the NiO material itself and the researchers have re-focussed our efforts on finding a replacement transparent p-type semiconductor. The group’s strategy and recent results will be presented. Recent work to expand the applications to photoelectrochemical water splitting for energy storage will be described, briefly [6].
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EA Gibson, AL Smeigh, L Le Pleux, L Hammarström, F Odobel, G Boschloo, A Hagfeldt., Angew. Chem Int Ed 2009, 48, 4402 –4405.
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J He, H Lindström, A Hagfeldt, S Lindquist, J Phys Chem B, 1999, 103, 8940–8943.
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CJ Wood, GH Summers, EA Gibson. Chem Commun 2015, 51, 3915 – 3918.
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J-F Lefebvre, X-Z Sun, JA Calladine, MW George, EA Gibson. 2014, 50, 5258 – 5260. G Boschloo, EA Gibson, A Hagfeldt J Phys Chem Lett, 2011, 2, 3016–302. EA Gibson, L Le Pleux, J Fortage, Y Pellegrin, E Blart, F Odobel, A Hagfeldt, G Boschloo, Langmuir 2012, 28, 6485–6493.
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FA Black, CJ Wood, S Ngwerume, GH Summers, IP Clark, M Towrie, Jason E Camp, EA Gibson, Faraday Discussions, 2017, 198, 449 – 461. L D'Amario, R Jiang, U Cappel, EA Gibson, G Boschloo, H Rensmo, L Sun, L Hammarström, H Tian, ACS Appl Mater Interfaces. 2017, 9, 33470–33477.
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EA Gibson, Chem Soc Rev, 2017, 46, 6194 – 6209. N Põldme, L O’Reilly, I Fletcher, I Sazanovich, M Towrie, C Long, JG Vos, MT Pryce, EA Gibson Chem Sci In press.