Theoretical Investigation of Substituted End Groups in Thiophene-Phenyl-Thiophene (TPT) Derivatives for High Efficiency Organic Solar Cells

The field of organic solar cells has witnessed notable advancements in the past few years, mostly due to the development of novel materials for the active layer. The current investigations reveal the potential of nine previously unexplored molecules (TP1–TP9) designed by end group modification of TPT4F molecule. These molecules were investigated at MPW1PW91/6-31G (d, p) with DFT and TD-DFT approach to study the various photovoltaic and geometrical parameters. The results obtained through computations indicated improvement in the investigated parameters. The terminal group modification shifted the absorption maximum towards longer wavelength in the UV-visible region. Highly conjugated modified acceptors reduced the band gap. The lower excitation energies increased the rate of charge transfer. The designed molecules showed improved excited state lifetime in comparison to the reference. The open circuit voltage was determined using the PTB7 polymer, which exhibited a noticeable improvement, especially in TP1 (1.70 eV), TP3 (1.75 eV), TP4 (1.68 eV), TP6 (1.85 eV), and TP7 (1.75 eV) when compared with reference (1.59 eV). Moreover, charge transfer investigations of designed molecules with PTB7 complex were performed by analyzing the concentration of charge transfer over molecular orbitals, that is, HOMO to LUMO. All of the preceding investigations targeted to achieve high-efficiency organic cells reveal that the altered molecules can be considered effective candidates to tackle future energy problems.