Theoretical study of star shaped benzotriindole based variant non-fullerene acceptors for efficient organic solar cells

The current study presents six D-π-A configured non-fullerene acceptor chromophores (BTI1-BTI6) derived from benzotriindole compound end-capped with hexyldicyanovinyl groups, referred to as BTI (2 T-DCV-Hex)₃, through structural tailoring of different terminal acceptors. Optoelectronic characteristics of newly designed chromophores were determined via DFT study at B3LYP/6-31G (d,p) functional. Various analyses such as frontier molecular orbitals, density of states (DOS), transition density matrix (TDM), binding energy (E_b), and open circuit voltage (V_oc) were conducted. All the derivatives exhibited a comparable band gap (2.45–2.70 eV) manifesting absorption bands in the UV-Visible spectrum (590–463 nm), in solvent as well as in gaseous phase. Interestingly, smaller E_b values of 0.170 and -0.099 eV were observed for BTI5 and BTI6, respectively, suggesting a greater degree of charge transfer and improved exciton dissociation in these derivatives. These findings are further supported by TDM and DOS analyses, which confirm that all the studied compounds exhibit a higher charge transfer rate from highest occupied orbital to lowest unoccupied orbital (HOMO to LUMO). In conclusion, the good photovoltaic response observed for all the compounds suggests that these chromophores are reasonable candidates for development of efficient organic solar cells.