A theoretical approach to enhance light harvesting in dye-sensitized solar cells through strategic Ni-porphyrin dye modifications

Dye-sensitized solar cell (DSSC) is one of the most promising photovoltaic technologies due to its economically favourable cost and ease of fabrication. Porphyrin, having inherent property of light absorption, works as an important dye for use in solar cells. In this study, we have investigated the modifications of an experimentally reported dye, Nickel tetraphenylporphyrin cyanoacrylic acid (NiTPP-CAA) aiming at enhancing light absorption and overall efficiency of the dye by the insertion of furan and thiophene spacers between the tetraphenylporphyrin core and the cyanoacryl anchoring acceptor. Density functional theory (DFT) and time-dependent DFT (TD-DFT) have been employed to investigate diverse topologies of these heterocyclic rings, emphasizing the influence of distinct combinations of spacers on photovoltaic parameters. This demonstrates that dyes with more heterocyclic ring spacers have a lower HOMO-LUMO energy gap, which speeds up charge transfer. The results also indicate that dyes with mixed furan and thiophene spacers perform better. These mixed combinations of spacers, especially those with alternating furan and thiophene, show a synergy of balanced strong electron-withdrawing ability with enhanced conjugation, leading to improved light-harvesting efficiency and better charge separation. In addition to improving electron transfer efficiency, these mixed spacers lower the HOMO-LUMO energy gap. These dyes show great promise for increasing DSSC efficiency due to the smart utilization of mixed spacers, as we have seen significant enhancements in the light harvesting efficiency (LHE), open-circuit voltage (V_oc) and excited state lifetime (τ). This discovery paves the path for future research in optimizing dye design for sustainable solar energy applications.