Tunable optoelectronic properties of D-A-π-A type dyes by altering auxiliary acceptor position and atomic electronegativity

Abstract

The reasonable molecular design is an effective approach to improve the power conversion efficiency of DSSCs. Various auxiliary acceptors have been synthesized and employed for D-A-π-A type dyes in recent years. However, the effects of auxiliary acceptor position and atomic electronegativity on the performance is still unclear. On account of these, the two type dyes were designed and theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) aiming at revealing structure-property relationships. The results illustrate that type II dyes with the auxiliary acceptor near acceptor have the better intramolecular charge transfer (ICT) character and they will exhibit better open-circuit photovoltage (VOC) and the short-circuit photocurrent density (JSC) due to larger molar extinction coefficients (ε), light harvesting efficiency (LHE), electronic injection driving force (ΔGinject), and vertical dipole moment (μnormal). With the decreased atomic electronegativity, the absorption properties of dyes will be improved and electron recombination can be suppressed, which will lead to better conversion efficiency. This theoretical study is expected to provide new strategies to synthesize promising dyes.