The plant pigment betanin is investigated as a dye-sensitizer on TiO₂ with regard to its potential to undergo twoelectron oxidation following one-photon excitation. Electrochemical, spectroelectrochemical and transient absorption measurements provide evidence for two-electron proton-coupled photo-oxidation leading to a quinone methide intermediate which rearranges to 2-decarboxy-2,3-dehydrobetanin. Time-resolved spectroscopy measurements of betanin on nanocrystalline TiO² and ZrO₂ films were performed on femtosecond and nanosecond time-scales and provide evidence for transient species with absorption bands in the blue and the red. The results shed light on previous reports of high quantum efficiencies for electron injection and point the way to improved solar conversion efficiency of organic dyesensitized solar cells.

Date Published: 9 September 2014
PDF: 9 pages
Proc. SPIE 9165, Physical Chemistry of Interfaces and Nanomaterials XIII, 91650N (9 September 2014); doi: 10.1117/12.2063888

Published in SPIE Proceedings Vol. 9165:
Physical Chemistry of Interfaces and Nanomaterials XIII
Natalie Banerji; Sophia C. Hayes; Carlos Silva, Editor(s)