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Abstract To improve the efficacy of organic solar cells (OSCs), novel small acceptor molecules (CTD1–CTD7) were designed by modification at the terminal acceptors of reference compound CTR. The optoelectronic properties of the investigated compounds (CTD1–CTD7) were accomplished by employing density functional theory (DFT) in combination with time-dependent density functional theory (TD-DFT). The M06 functional along with a 6-311G(d,p) basis set was utilized for calculating various parameters such as: frontier molecular orbitals (FMO), absorption maxima (λ max), binding energy (E b), transition density matrix (TDM), density of states (DOS), and open circuit voltage (V oc ) of entitled chromophores. A red shift in the absorption spectra of all designed chromophores (CTD1–CTD7) was observed as compared to CTR, accompanied by low excitation energy. Particularly, CTD4 was characterized by the highest λ max value of 685.791 nm and the lowest transition energy value of 1.801 eV which might be ascribed to the robust electron-withdrawing end-capped acceptor group. The observed reduced binding energy (Eb) was linked to an elevated rate of exciton dissociation and substantial charge transfer from central core in HOMO towards terminal acceptors in LUMO. These results were further supported by the outcomes from TDM and DOS analyses. Among all entitled chromophores, CTD4 exhibited bathochromic shift (685.791 nm), minimum HOMO/LUMO band gap of 2.347 eV with greater CT. Thus, it can be concluded that by employing molecular engineering with efficient acceptor moieties, the efficiency of photovoltaic materials could be improved.

To improve the efficacy of organic solar cells (OSCs), novel small acceptor molecules (CTD1–CTD7) were designed by modification at the terminal acceptors of reference compound CTR. The optoelectronic properties of the investigated compounds (CTD1–CTD7) were accomplished by employing density functional theory (DFT) in combination with time-dependent density functional theory (TD-DFT). The M06 functional along with a 6-311G(d,p) basis set was utilized for calculating various parameters such as: frontier molecular orbitals (FMO), absorption maxima (λmax), binding energy (Eb), transition density matrix (TDM), density of states (DOS), and open circuit voltage (Voc) of entitled chromophores. A red shift in the absorption spectra of all designed chromophores (CTD1–CTD7) was observed as compared to CTR, accompanied by low excitation energy. Particularly, CTD4 was characterized by the highest λmax value of 685.791 nm and the lowest transition energy value of 1.801 eV which might be ascribed to the robust electron-withdrawing end-capped acceptor group. The observed reduced binding energy (Eb) was linked to an elevated rate of exciton dissociation and substantial charge transfer from central core in HOMO towards terminal acceptors in LUMO. These results were further supported by the outcomes from TDM and DOS analyses. Among all entitled chromophores, CTD4 exhibited bathochromic shift (685.791 nm), minimum HOMO/LUMO band gap of 2.347 eV with greater CT. Thus, it can be concluded that by employing molecular engineering with efficient acceptor moieties, the efficiency of photovoltaic materials could be improved. [ABSTRACT FROM AUTHOR]

Keeping in view, the recent energy conditions and contribution of non-fullerene acceptors (NFAs) towards organic solar cells (OSCs), a series of NFAs (D1-D9) was designed. The novel fused ring NFAs (D1-D9) having A-D-A architecture were designed by structural engineering of R molecule with effective benzothiophene based acceptor moieties. For current study, all the calculations were accomplished at M06/6-311G (d,p) level. Different computational approaches like density of states (DOS), binding energy (Eb), transition density matrix (TDM), absorption spectra (UV–Vis), electronic properties (FMOs) and open circuit were performed to investigate the photovoltaic response of newly designed D1-D9 chromophores. The terminal substitution of end-capped acceptors exhibited a reduction in energy gap (ΔE = 2.222–1.986 eV) with high electron mobility rate in all the derivatives (D1-D9) than that of R. All the designed chromophores exhibited wider absorption spectrum (λmax = 845.039–786.552 nm) along with lower excitation energy as compared to R (λmax = 770.040 nm) except D1 and D9. Interestingly, lower binding energy (Eb = 0.419–0.473 eV) accompanying with higher excition dissociation rate was seen in derivatives than that of reference compound. Moreover, a comparable value of Voc was noted in derivatives when calculated via LUMOacceptor–HOMOPBDBT. Among all fore-said chromophores (D1-D9), D4 exhibited lowest binding energy and thus ensured easier and faster excition dissociation rate along with highest Voc (1.586 V). In cessation, this structural modification by utilizing various acceptors played a significant role in obtaining auspicious photovoltaic response in compounds. Hence, our study encourages the experimentalists for synthesizing these proposed organic systems for the attaining high efficacy photovoltaic devices.