New Triphenylamine-Based Organic Dyes with Different Numbers of Anchoring Groups for Dye-Sensitized Solar Cells

Abstract

We synthesized two organic dyes (TPA–CN1–R2 and TPA–CN2–R1) based on the TPA core unit having structure A–D–A, which contain the triphenylamine moiety as an electron donor and both cyanovinylene 4-nitrophenyl and carboxylic (anchoring) units as electron acceptors. Nanocrystalline TiO2-based dye-sensitized solar cells (DSSCs) were fabricated using these dyes to investigate the effect of number of anchoring groups on their photovoltaic performance. The DSSCs based on TPA–CN1–R2 and TPA–CN2–R1 showed power conversion efficiency (PCE) of about 2.36% and 1.41%, respectively. The PCE has been significantly improved up to 4.37% and 2.8%, upon addition of 20 mM deoxycholic acid (DCA) to the dye solution for TiO2 sensitization. Coadsorption of DCA decreased dye coverage but significantly improved the value of the short-circuit photocurrent (Jsc). The breakup of π-stacked aggregates might improve the electron injection yield and thus Jsc. Electrochemical impedance spectra and current–voltage characteristics in the dark indicate that the electron lifetime was improved by coadsorption of DCA, accounting for the significant improvement of open-circuit voltage (Voc).