Investigation of the influence of donor and internal acceptor on photovoltaic parameters in D-A1-π-A Dye sensitizers for efficient DSSCs

In dye-sensitized solar cells (DSSCs), the efficiency of light-to-electricity conversion is significantly influenced by the choice of donor and internal acceptor units in the dye molecules. In this study, we have designed and investigated the impact of donor groups and internal acceptor units for emphasizing the performance of DSSCs. The performance of the D-A¹-π-A system has been evaluated in terms of various photovoltaic parameters such as the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), HOMO-LUMO energy gap (HLG), excited-state oxidation potential (E_dye*), free energy of electron injection (G_inj), and open-circuit voltage (V_OC). DFT and TDDFT methodology is used to examine dye's electronic properties, including charge transfer dynamics, energy gaps, and photovoltaic parameters and to determine how these combinations influence light absorption, electron injection, and overall cell efficiency. Our findings indicate that D-A¹-π-A architectural dyes enhance light absorption spectra ranging from 309 nm to 523 nm with variation in donor and acceptor groups and facilitating more effective electron transfer to the TiO₂ semiconductor and enhancing the overall cell efficiency. Among all the studied dyes, the R4 dye containing substituted carbazole and benzotriazole unit shows a maximum efficiency of 4.48 % at a J_SC value of 15 mA cm^-2. Hence, this research showed the importance of molecular design of organic dyes and provided insights into the development of next-generation dyes for solar energy applications.