Study of the microscopic mechanism of stepwise charge injection in co-sensitive DSSCs in the framework of a D–π–A dye and chlorophyll

Abstract

The newly synthesized dye molecules TY6 and CXC22 were selected to explain the influence of anthracene and acetylene groups on the power conversion efficiency (PCE) of the molecules at the microscopic level. Theoretical simulation was carried out to understand the properties of the two molecules, including frontier molecular orbitals, absorption spectra, light absorption efficiency, intramolecular charge transfer (ICT), dye regeneration, I–V prediction, etc. The results suggest that for CXC22, adding an anthracene and acetylene group in the conjugate bridge greatly enhances the molecule's absorption wavelength and molar extinction coefficient; CXC22 also has significant advantages in the intramolecular charge transfer and comparatively better dye regeneration and electron injection. These parameters cause CXC22 to have a higher PCE. Subsequently, CXC22 and the chlorophyll molecule (CHL7) were selected for co-sensitization to regulate performance. The stable structure in the co-sensitization configuration was screened, and the absorption spectrum characteristics and charge transfer mechanisms were revealed for the co-sensitization system. The designed evaluation model predicted that the PCE of CO1 (the cosensitive system of CXC22 and TY6 in H–H configuration is referred to as CO1) could reach 16.78%. This work provides an idea for developing an efficient dye-sensitized solar cell system.