Theoretical investigation of novel tetrathiafulvalene-triphenylamine sensitizers

Abstract

Two novel sensitizers with D-D-π-A (YD2) and 2D-D-π-A (YD3) structures were designed by introducing different numbers of tetrathiafulvalene (TTF) unit as the auxiliary electron donor based on the simple D-π-A triphenylamine sensitizer (YD1) to enhance the electron donating ability. The geometries, electronic structures, and optical properties of YD1－3 before and after binding to TiO2 clusters were investigated. Owing to introduction of TTF unit, YD2 and YD3 show larger steric hindrance and a narrower band gap than YD1. Moreover, the estimated light-harvesting efficiency (LHE), injection driving force (ΔGinject) values, and density of states (DOS) calculations indicate that YD2 and YD3 should show higher short-circuit photocurrent density (Jsc) and open-circuit photovoltage (Voc) than YD1 with the presence of TTF unit. All of the results indicate that TTF unit can be used as an auxiliary electron donor in organic sensitizers to improve their photovoltaic properties.