Amino-based Anthocyanin Dyes: Exploring the Relation Between Structural Rigidification and Back-Electron Transfer
Ana Lucia Pinto a, Patríca Máximo a, João Pina b, Giuseppe Calogero c, César A. T. Laia a, A. Jorge Parola a, J. Carlos Lima a
a LAQV-REQUIMTE, Chemistry Department, NOVA School of Science and Technology, Campus de Caparica, 2829-516, Caparica, Portugal.
b University of Coimbra, Coimbra Chemistry Centre, Department of Chemistry, Rua Larga, 3004-535 Coimbra, Portugal.
c CNR, Instituto per i Processi Chimico-Fisici, Sede di Messina, Salita Sperone, C. da Papardo, I-98158 Faro Superiore Messina, Italy.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Contributed talk, Ana Lucia Pinto, presentation 135
Publication date: 20th April 2022

The use of natural/bio-inspired pigments as sensitizers in Dye-Sensitized Solar Cells (DSSCs) has come to be a worthwhile substitute to the inorganic/organic sensitizers due to the cost-effectiveness enhancement and reduced environmental pollution risks.[1] The first reported DSSC using a natural anthocyanin (cyanidin-3-O-glucoside) displayed a conversion yield of 0.56 % and paved the way for sustainable DSSCs based on renewable resources.[2] The structural modification of this natural compound, through the insertion of a stronger electron-donating moiety (7-diethylamino-3’,4’-dihydroxyflavylium), led to an improved efficiency of 2.15 %, proving the potential of bio-inspired compounds for energy applications.[3] Herein, a series of new amino-based flavylium derivatives inspired in compound 7-diethylamino-3’,4’-dihydroxyflavylium were designed and synthesized, focusing on studying the impact of rigidifying the flavylium structure, as well as the structure of the electron-donating moiety, by replacing diethylamine by a julolidine moiety. Despite being a stronger electron-donor, the current intensity vs. potential properties of photoanodes containing these dyes presented lower photocurrent for julolidine-based compounds, possibly attributable to the presence of increased back-electron transfer (BET). These results pointed to evidence that has been overlooked in the study of anthocyanin derivatives in energy applications, that is the impact of the structure in the back-electron transfer processes that might hinder the photocurrent. This is the first study that puts in evidence how BET processes can affect the performance of this family of compounds.

FCT/MCTES is acknowledged for financial support through the project PD/00184/2012/PDQS, the grant PD/BD/135087/2017 (ALP) and the Associate Laboratory for Green Chemistry- LAQV (UIDB/50006/2020 and UIDP/50006/2020).

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