Effects of Structural Modification on the Photoelectrical Properties of the D-A-π-A-Type Dyes in DSSCs: A Computational Investigation

摘要

The structure-activity relationships of the three D-A-π-A type dyes (LC6, LC7 and LC8) were investigated via density functional theory (DFT) and time-dependent DFT methods. The results indicate the substitution of thiophene with benzene ring as π spacer has intensified the distortion in the structure of LC8, which will ease the aggregation of dye on the photo-cathode. The greatest shift of the conduction band of TiO2, driving force of electron injection, excited state lifetime and lowest lateral intermolecular charge transfer rate of LC8 leads to the prominent photoelectrical properties among the three dyes. In addition, three novel dyes (LC81, LC82 and LC83) were designed via introducing a -CN group into the structure of LC8. The obtained results imply that the designed dye LC81 would exhibit the outstanding photoelectrical characteristics among LC8 and its derivatives, owing to its lowest energy gap, chemical hardness, and the greatest polarizability, total first hyperpolarizability, electrophilicity and electroaccepting power, which can provide a theory evidence for the experimental synthesis of dyes with better efficiency.