Theoretical investigation and design of high-efficiency dithiafulvenyl-based sensitizers for dye-sensitized solar cells: the impacts of elongating π-spacers and rigidifying dithiophene

摘要

DSSCs have been extensively investigated in the past decade, and the search for more efficient dyes for DSSCs remains challenging. In this work we discuss the influences of elongating π-spacers and rigidifying dithiophene on the performance of dithiafulvenyl (DTF)-based organic dyes using density functional theory (DFT) and time-dependent DFT methods. We show that systematically elongating the 7t-spacer of the DTF-2P dye by increasing the number of thiophene groups tends to red-shift the absorption peak and broaden the absorption range, thus improving the light-harvesting efficiency of DTF-2P-T and DTF-2P-2T. Furthermore, among the three dyes, DTF-2P-T would have the best performance because it performs nicely on the key parameters including the electron injection driving force (D), the light-harvesting efficiency (LHE), and the shift of the TiO2 conduction band (△E_(cb)). In particular, DTF-2P-2T has a larger LHE despite the smaller D and △E_(cb) compared with DTF-2P-T. Having realized the great merits of modification on π-spacers, afterwards, we designed a novel dye by rigidifying the dithiophene moiety of DTF-2P-2T.