Molecular Engineering and Theoretical Investigation of Novel Metal-Free Organic Chromophores for Dye-Sensitized Solar Cells

Abstract

In this work we report design and synthesis of three new metal free D-D-A-?-A type dyes (E<inf>1-3</inf>) with different acceptor/anchoring groups, as effective sensitizers for nanocrystalline titanium dioxide based dye sensitized solar cells. All the three dyes carry electron donating methoxy group as an auxiliary and indole as a principal donor, cyanovinylene as an auxiliary acceptor and thiophene as a ?-spacer. Whereas, cyanoacetic acid, rhodanine-3-acetic acid and 4-aminobenzoic acid perform as acceptor/anchoring moieties, respectively in the dyes E<inf>1-3</inf>. Though the dye containing 4-aminobenzoic acid unit (E<inf>3</inf>) exhibits comparatively lower ?<inf>max</inf>, it shows the highest power conversion efficiency arising from the higher electron life time and good light-harvesting capability. The DFT studies reveal a better charge separation between the HOMO and LUMO levels of E<inf>3</inf>, further substantiating the experimental results. Among the three dyes, E<inf>3</inf> shows the best photovoltaic performance with short-circuit current density (J<inf>sc</inf>) of 9.35 mA cm-2, open-circuit voltage (V<inf>oc</inf>) of 620 mV and fill factor (FF) of 0.71, corresponding to an overall conversion efficiency of 4.12% under standard global AM 1.5G. © 2015 Elsevier Ltd. All rights reserved.