Synergistic charge-transfer dynamics of novel benzothiadiazole-based donor materials for higher power conversion efficiency: From structural engineering to efficiency assessment in non-fullerene organic solar cells

In the realm of organic solar cell technology, current research is dedicated to enhancing the photovoltaic properties of donor-π-acceptor (D-π-A) materials to achieve higher power conversion efficiencies (PCE). This optimization focuses particularly on fine-tuning the conduction band and electrolytic characteristics to maximize performance. Addressing the growing demand for novel materials with enhanced optoelectronic properties in organic photovoltaic research, our proposed compound BT05, one of nine new benzothiadiazole-based D-π-A donor molecules (BT01-BT09), exhibits a power conversion efficiency (PCE) of 25 %, surpassing the 18 % PCE of the reference compound BTD-OMe. TD-DFT and DFT simulations illuminate how donor modifications enhance the photovoltaic characteristics of the proposed molecules. Higher open-circuit voltage (V_OC) of 1.74–2.26 V, increase in binding energy (∼1.997), λ_max (470–476 nm), reduction in energy gap (4.25–4.65 eV), also validates the PCE results and confirm the usefulness of designed molecules (BT01-BT09). Moreover, D_HOMO and A_LUMO, TDM, reorganization energy λ_e (0.0124–0.0134) and λ_h (0.0094–0.0098), and NPA results also confirm that BT01-BT09 molecules unlock the organic solar cell's potential and advance sustainable energy solutions through innovative technology. Among all developed compounds, BT05 displays higher V_OC (2.26 V), 87 % fill-factor, and 25 % PCE; hence, it is recommended in future solar cell applications.