In Silico Designing of Thieno[2,3- b ]thiophene Core-Based Highly Conjugated, Fused-Ring, Near-Infrared Sensitive Non-fullerene Acceptors for Organic Solar Cells.

The performance of organic solar cells (OSCs) has been improving steadily over the last few years, owing to the optimization of device fabrication, fine-tuning of morphology, and thin-film processing. Thiophene core containing fused ring-type non-fullerene acceptors (NFAs) achieved significant proficiency for highly efficient OSCs. Quantum chemical computations are utilized herein with the motive of suggesting new NIR sensitive, highly efficient low-band gap materials for OSCs. A series of extended conjugated A-π-D-π-A architectured novel fused-ring NFAs (FUIC-1-FUIC-6) containing thieno[2,3- b ]thiophene-based donor core are proposed by substituting the end-capped units of synthesized molecule F10IC. Different properties including frontier molecular orbital analysis, density of states analysis, transition density matrix analysis, excitation energy, reorganizational energies of both holes (λ h ) and electrons (λ e ), and open-circuit voltage ( V oc ) were performed employing the density functional theory approach. Charge transfer analysis of the best-designed molecule with the donor complex was analyzed to comprehend the efficiency of novel constructed molecules (FUIC-1-FUIC-6) and compared with the reference. End-caped acceptor alteration induces the reduction of the energy gap between HOMO-LUMO (1.88 eV), tunes the energy levels, longer absorption in the visible and near-infrared regions, larger V oc , smaller reorganizational energies, and binding energy values in designed structures (FUIC-1-FUIC-6) in comparison to reference (FUIC). The designed molecules show the best agreement with the PTBT-T donor polymer blend and cause the highest charge from the HOMO to the LUMO orbital. Our findings predicted that thieno[2,3- b ] thiophene-based newly designed molecules would be efficient NFAs with outstanding photovoltaic characteristics and can be used in future applications of OSCs.