Enhanced photovoltaic properties via end-capped acceptor moieties with quinoidal selenophene π-spacer: probed by DFT/TD-DFT

Quinoidal π–conjugated chromophores have received growing attention in recent decades owing to their strong structure–property relationships and intrinsically key electronic properties. Herein, new A–π–A configuration-based compounds (BzTQD1-BzTQD8) were designed from BzTQR reference compound by end-capped acceptor modification. The selenophene π-spacers were incorporated into the backbone to enhance intramolecular charge transfer (ICT). The density functional theory (DFT) approach was used to investigate their optoelectronic and photovoltaic characteristics at the M06/6-311G(d,p) level. Interestingly, the afore-mentioned chromophores showed improved charge transfer and lower energy gaps (2.2–2.3 eV). They also displayed bathochromic absorption shifts in solvent (700.5–725.9 nm) and gas phases (652.5–671.9 nm) with lower excitation energies, correspondingly. Further, the TDM and DOS showed that structural tailoring of the designed molecules significantly enhanced the charge separation in them. Furthermore, the exciton binding energies (Eb) ranging from 0.4 to 0.5 eV, indicated greater rate of exciton dissociation in these compounds. Among all the designed compounds, BzTQD1 and BzTQD7 displayed the least energy gaps (2.2 eV). In particular, BzTQD7 exhibited the most red-shifted λmax (725.9 nm) and a comparatively low Eb (0.5 eV). To probe photovoltaic behavior, the designed acceptors were blended with the PTB7 donor polymer, achieving promising open-circuit voltage (Voc). Overall, this work demonstrates that the quinoidal designed π–conjugated materials might be efficient for next generation organic solar cells.