End-cap modeling on the thienyl-substituted benzodithiophene trimer-based donor molecule for achieving higher photovoltaic performance.

Despite the substantial advancements in organic solar cells (OSCs), the best devices still have quite low efficiencies due to less focus on donor molecules. With the intention to present efficient donor materials, seven small donor molecules (T1-T7) were devised from DRTB-T molecule by using end-capped modeling. Newly designed molecules exhibited remarkable improved optoelectronic properties such as less band gap (from 2.00 to 2.23 eV) than DRTB-T having band gap of 2.57 eV. Similarly, a significant improvement in λ values was noticed in designed molecules in gaseous medium (666 nm-738 nm) and solvent medium (691 nm-776 nm) than DRTB-T having λ values at 568 nm and 588 nm in gas and solvent phase respectively. Among all molecules, T1 and T3 exhibited significant improvement in optoelectronic properties such as narrow band gap, lower excitation energy, higher λ values and lower electron reorganization energy as compared to pre-existed DRTB-T molecule. The better functional ability of T1-T7 is also suggested by an improvement in open circuit voltage (Voc) of designed structures (1.62 eV-1.77 eV) as compared to R (1.49 eV) when PCBM is used as an acceptor. So, all our newly derived donors can be employed in the active layer of organic solar cells to manufacture efficient OSCs.