DFT insights into the photovoltaic performance of A–π–A non-fullerene acceptors for organic solar cells

Recent advances in the non-fullerene acceptors (NFAs) have achieved remarkable attention owing to their significant photovoltaic and optoelectronic characteristics in organic solar cells. Herein, new A–π–A configuration-based NFAs (TPBD-Cl to TPBD-CF3) were designed by incorporating the strong electron withdrawing acceptor units at their terminals. Theoretical investigation was performed for these chromophores by using DFT/TD-DFT methods at M06/6-311G(d, p) level. The results demonstrate that the end-capped acceptor substitution has promoted the charge transfer and efficiently reduced the energy gap (2.25–2.13 eV). Further, it was revealed that the structural modifications elevated that absorption wavelengths in the studied chromophores (721.97–754.58 nm). The transition density matrix (TDM) and density of states (DOS) analyses demonstrated an efficient charge transfer from the donor (π–spacer) moieties towards terminal acceptors. Notably, TPBD-NO2 compound exhibited the least energy gap (2.13 eV), highest absorption wavelength (λmax = 754.58 nm) and correspondingly least excitation energy (1.64 eV). Moreover, it showed the minimal exciton binding energy (0.50 eV) among all other derivatives which highlight its potential for the organic solar cell materials. Photovoltaic parameters were calculated by blending the donor (PBDB-T) with designed acceptors showed the good open-circuit voltages (Voc). These findings suggest that the end-capped engineering in NFAs chromophores can significantly enhance the optoelectronic performance, offering promising materials for next-generation OSC devices.