Design and analysis of diisobutoxybenzodithiophene based donor for application in organic solar cell: DFT and TD-DFT Study

The newly designed chromophores (BT1-BT7) of the highly unsaturated donor-acceptor (D-A) were theoretically analyzed and recommended for applications in organic solar cells (OSCs). Conjugated A-groups have been replaced in the reference (BTR) during its design. The structural and optoelectronic properties of designed molecules were calculated using density functional theory (DFT) and Time-dependent DFT (TD-DFT) techniques. The frontier molecular orbitals (FMO) study revealed that BT7 has the lowest energy gap of 2.01 eV, which has significantly less than BTR (2.34 eV), and a significant amount of charge transfer (CT) between HOMO and LUMO has been observed. Out of all the newly designed chromophores in chloroform, the highest absorption spectra were found in the visible region with a bathochromic shift up to 768 nm. The dipole moment values of all the new chromophores (BT1-BT7) were significantly higher than the BTR (5.46 D), which resulted in good solvation. ESP analysis revealed electron distribution on various parts of the molecules by colored maps that are found to be effective for better ICT. The electron transition density resulting from light absorption at different chemical sites was shown using TDM plots. The electron and hole reorganization energy (RE) values were proved as highly efficient in promoting charge mobility and hindered charge recombination for new compounds. By scaling our designed donor to the recognized acceptor Y6, which has demonstrated the creation of OSCs, the open circuit voltage of each molecule was ascertained. The designed molecules exhibited higher open circuit voltages than the reference, indicating improved and fine-tuned optoelectronic properties that would aid in the development of solar cell devices in the future.