A computational finding on the effect of π-conjugated acceptors in thiophene-linked coumarin dyes for potential suitability in DSSC application

Abstract
Herein we studied the potential suitability of four thiophene-linked coumarin dyes in dye�sensitized solar cells (DSSCs) application by employing density functional theory (DFT) and
time-dependent DFT methods. The new four dyes comprise various π-conjugated acceptor moieties, such as quinazolinone-N-acetic acid, indoline carboxylic acid, rhodanine acetic acid,
and homophthalimide-N-acetic acid with dialkylamino coumarin as donor and thiophene as a common spacer. We have investigated the influence of the π-conjugated acceptor moieties in thiophene-linked coumarin dyes on the photovoltaic performance and adsorption onto the TiO2 surface. The π-conjugation in the acceptor moiety enhanced the intensity of the ICT band and which has been corroborated by the NBO data. C3 dye showed higher charge separation (∆q D–A
) between the coumarin donor and rhodanine acetic acid acceptor moieties and which revealed a higher red-shift in the absorption spectra for C3 dye. The photophysical,
electrochemical properties and photovoltaic parameters of DSSCs have been calculated to assess their suitability for the application in DSSCs. The higher dye regeneration driving force,
higher lifetime, and higher power conversion efficiency values (calculated) make dye C3 the potential candidate for DSSCs among all the studied dyes