Development of heterocyclic D-pi-A dyes for application in efficient and stable thin-layer Dye-Sensitized Solar Cells

In recent years, our research activity has been mainly focused on the design and synthesis of new organic dyes, featuring different heterocyclic groups, with potential applications as DSSC sensitizers. In general, the compounds prepared in our laboratories were based on the classical D-pi-A architecture, with a donor and an acceptor moiety joined by a conjugate spacer.[1] We have explored the possibility to introduce different structural units in all three sections of the molecules (see Figure), aiming to improve their light absorption properties as well as their photochemical and anchoring stability, with the final objective to obtain more efficient and stable devices even under simple fabrication conditions. For example, we have introduced dyes featuring a thiazolo[5,4-d]thiazole central unit,[2] and demonstrated that they can attain up to 7.71% efficiency in thin-layer, transparent DSSCs.[3] Furthermore, we have synthesized compounds bearing pyridine-carboxylic acids and pyridine-N-oxides as anchoring groups, and demonstrated their superior anchoring stability compared to their cyanoacrylate-based counterparts.[4] In this communication, we will present the synthesis of our latest compounds, and discuss how structural modifications influence their optical properties as well as the stability of their attachment to TiO2. In addition, we will present our studies on the fabrication and testing of DSSCs built using the new sensitizers, highlighting our best results both in terms of device efficiency and stability. References [1]Ooyama, Y.; Harima, Y. ChemPhysChem 2012, 13, 4032. [2]Dessì, A. et al., Eur. J. Org. Chem. 2013, 1916. [3]Dessì, A. et al., Chem. Commun. 2014, DOI: 10.1039/c4cc06160h. [4](a) Cecconi, B. et al., Asian J. Org. Chem. 2014, 3, 140; (b) Franchi, D. et al., Tetrahedron 2014, 70, 6285.