Tönu Pullerits

System co-sensitization and extension of the π-conjugated system are recognized as two key strategies for improving the performance of dye-sensitized solar cells (DSSCs). In this study, density functional theory (DFT) was employed to simulate two experimentally synthesized molecules, RK1 and D205, and to evaluate the performance of their co-sensitization system. Furthermore, molecular design was conducted based on the RK1 framework by extending the π-conjugated bridge. As a result, the microscopic mechanism responsible for the enhancement of DSSC performance through system co-sensitization and π-conjugated system extension is systematically explored. Structural and performance evaluations of the individual dyes reveal the intrinsic factors contributing to the superior photoelectric properties of the RK1 molecule. Considering the complementary nature of their absorption spectra, a co-sensitization analysis was subsequently performed. The results demonstrate that the co-sensitized system exhibits enhanced light-harvesting efficiency, leading to improved photoelectric performance compared to the individual dye systems. Comparative analyses of different co-sensitization configurations (H-H and H-T) indicate that the H-H configuration possesses superior optical properties and a more efficient charge separation rate, making it a more suitable configuration for co-sensitization. Additionally, the analysis of the designed molecules shows that an extended π-bridge significantly improves molecular planarity, broadens the spectral response, and enhances charge transfer efficiency. Consequently, the modified dye exhibits a higher photoelectric conversion efficiency (PCE). These findings provide meaningful theoretical guidance for the design and development of high-performance DSSCs.