Computational Insights into the Fusion of Thiophene to Aza BODIPY Based Molecules for Better Organic Solar Cell Applications

Unleashing the potential of organic solar cell (OSC) research drives advancements in renewable energy, paving the way for accessible, affordable, and sustainable solar power aiming to meet the global energy needs of the century. The knowledge on the structure-property relationship is essential of the potential organic molecules to improve the efficiency, stability, and reliability of OSC molecules. The recent research works suggest that thiophene based Fluorinated Boron-Dipyrromethene (BODIPY) molecules have the potential to improve the efficiency and performance of organic solar cells and therefore we have designed and studied seven new 4,4-difluoro-1,3,5,7-tetrathienyl-4-boron-3a,4a,8-triaza-s-indacene (DT) molecules by fusing thiophene unit(s) using Density functional theory (DFT) and Time-dependent density-functional theory (TDDFT) calculations for their optoelectronic properties. Our results reveal that site specific incorporation of thiophene units bring enhanced absorption and emission maxima (up to 902.42 nm and 958.91 nm respectively) for the designed DT molecules with reduced HOMO-LUMO gaps. Optimized geometries tell that there is an excellent π-delocalization along with stabilizing weak interactions dictating the planarity of these molecules. The computed optoelectronic properties such as light harvesting efficiency, Transition density matrix, reorganization energy, hole and electron transport properties indicate that these designed molecules tend to show better characteristic features compared to the experimentally reported DT molecule. Introducing electron deficient groups like nitrobenzene has a little effect on the optoelectronic properties of DT derivatives. Overall, this study provides insights into the effect of fusion of thiophene units at different positions on aza-BODIPY derivative in the optoelectronic properties of DT molecules and provides valuable clues for further investigation in utilizing them to produce organic solar cells with enhanced photovoltaic properties.