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EnglishIn this work, the use of cobalt redox electrolytes in partly covered photoelectrochromic devices is investigated experimentally for the first time. The fabricated devices consist of a conductive glass photoanode coated with an electrochromic WO3 film of optical quality, including a mesoporous TiO2 layer (sensitized by the MK2 organic dye) that covers 20% of the device area. The liquid electrolyte is composed of 0.22 M Co(II)(bpy)3(PF6)2, 0.5 M LiClO4 and 0.5 M 4-tert-butylpyridine. A platinized conductive glass cathode completes the cell set-up. The fabricated devices are almost transparent in the bleached state with a Tlum value above 50%. They exhibit coloration speeds in the order of minutes, with a maximum contrast ratio of 2.9:1 after 21 min of illumination at 1000 W m−2 under open circuit conditions (OC), and high reversibility to fully bleached state in short circuit conditions. They provide a maximum measured power conversion efficiency of 0.28% due to limitations imposed by conflicting requirements of the photovoltaic and electrochromic elements, which is nonetheless sufficient to drive the coloration process. Since only the reduced specie Co2+ is present, initial illumination under OC for 3 min at 1000 W m−2 is necessary, prior to measurements, to oxidize Co2+ to Co3+ through the dye regeneration process in the electrolyte. The higher recombination losses of the Co2+/3+ redox shuttle compared to I−/I3−, which lead to a considerable reduction in coloration depth 20 days post fabrication due to loss of photoelectrons at the WO3/electrolyte interface, are suppressed by the use of a 35 nm thick ZnS barrier deposited on top of WO3. Remarkably, it results in a stabilized contrast ratio of 1.5:1, 23 days post fabrication. In addition, the color coordinates of the present devices resemble those of typical electrochromics: they exhibit blue coloration, as a result of the lack of the absorbing iodine in the electrolyte that produces a green tint.
Photoelectrochromic devices with cobalt redox electrolytes / Dokouzis, A.; Bella, F.; Theodosiou, K.; Gerbaldi, C.; Leftheriotis, G.. - In: MATERIALS TODAY ENERGY. - ISSN 2468-6069. - ELETTRONICO. - 15:(2020), pp. 100365-1-100365-8. [10.1016/j.mtener.2019.100365]
| Titolo: | Photoelectrochromic devices with cobalt redox electrolytes | |
| Autori: | ||
| Data di pubblicazione: | 2020 | |
| Rivista: | ||
| Digital Object Identifier (DOI): | http://dx.doi.org/10.1016/j.mtener.2019.100365 | |
| Appare nelle tipologie: | 1.1 Articolo in rivista |
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| File | Descrizione | Tipologia | Licenza | |
|---|---|---|---|---|
| 311) A. Dokouzis et al., Mater. Today Energy 15 (2020) art. no. 100365.pdf | 2a Post-print versione editoriale / Version of Record | Non Pubblico - Accesso privato/ristretto | Administrator Richiedi una copia | |
| MTENER_2019_127_R1.pdf | 2. Post-print / Author's Accepted Manuscript |  | Visibile a tuttiVisualizza/Apri |
http://hdl.handle.net/11583/2802019
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