Rational design of ZL003-based organic dyes for highly efficient dye-sensitized solar cells: Influence of alkynyl group and π-spacers on photovoltaic performance

Abstract

Dye-sensitized solar cells (DSSCs) have displayed huge potential in inexpensive, efficient, and clean solar energy-technology. To achieve highly efficient DSSCs, a series of D-π-A organic dyes were designed and their optoelectrical properties were calculated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Compared with ZL003, ZS1 designed by introducing the triple bond between donor and π bridge, has higher conjugation, narrower HOMO-LUMO bandgap, and extended absorption spectra. Then five new organic dyes were designed by substituting benzothiadiazole part of ZS1 with five electron-deficient heterocycles. The designed dyes have more conjugated structure, which leads to stronger light harvesting ability with the absorption spectra expanding to the near infrared region, the maximum absorption wavelength red shifting 78 nm∼448 nm and light harvesting efficiency (LHE) curve broadening obviously. The intermolecular electron transfer (IET) rate of the design dye is much faster than that of ZL003, over 85.3% of electrons in the design dye have been injected into TiO2 within 200 fs. Especially, the power conversion efficiency (PCE) of BBTD, BTTD and BZOD is more than 25.7%, mainly reflected in the obvious jump of the theoretical short current density (Jscpred.) by more than 68%. Therefore, the design dyes have a good application prospect. We believe that this work could provide theoretical guidance for the design of potential organic sensitizers in highly efficient DSSCs.