4-Methoxy-1,3-thiazole based donor-acceptor dyes: Characterization, X-ray structure, DFT calculations and test as sensitizers for DSSC

Abstract

Four donor-(π-conjugated-bridge)-acceptor type dyes A-D were designed and synthesized. These new compounds use an unconventional 4-hydroxy-1,3- thiazole building block as an additional chromophore for light harvesting and to extend the π-conjugated system of the molecules. The synthetic route involved a double N-arylation Hartwig-Buchwald reaction using Pd(dba) 2 as precatalyst and P( tBu) 3 as ligand. Two different triarylamines and a 4-methoxyphenyl group were used as electron donor moieties. The electron acceptor (anchoring) group was 2-cyanoacrylic acid for all dyes, whereas the π-spacer was varied and the influence was investigated. The dyes were thoroughly characterized using photophysical and electrochemical methods and by density functional theory calculations. Additionally, they were evaluated in nanocrystalline TiO 2-based dye-sensitized solar cells (DSSCs). The DSSCs were prepared with and without deoxycholic acid (DCA) as a co-adsorbent to inhibit dye aggregation. The efficiencies obtained were low for DSSCs fabricated without DCA, but were significantly improved for DCCS with co-adsorbed DCA. Additionally, the X-ray structure of dye D was obtained, demonstrating the stereochemistry and planar geometry of the molecule. The DSSC based on dye A showed an efficiency of η = 1.70% (J sc = 4.49 mA cm -2, V OC = 0.61 V, FF = 0.62) under 100 mW cm -2 simulated AM 1.5 G solar irradiation compared to η = 4.1% of the standard N 3 obtained under same conditions. © 2012 Elsevier Ltd. All rights reserved.