Structural tailoring via end-capped acceptors of thiophene-based C-shaped non-fullerene compounds with A-π-A backbone for the exploration of photovoltaic response

Abstract

In the current era, non-fullerene based electron acceptors show remarkable contribution to develop organic solar cells (OSCs) with maximum possible efficiency via improving their optoelectronic properties. Thus, in current report, eight novel A-π-A type dithieno[3,2-b:2′,3′-d]thiophene (DTh) core-based C-shaped non-fullerene acceptors (ETMM1–ETMM8) were designed theoretically by taking ETMMR as reference to achieve highly proficient photovoltaic materials. Hence, a comprehensive density functional theory (DFT) analysis was accomplished by employing B3LYP level in conjunction with 6-311G(d,p) basis set to determine the enhancement of optical as well as photochemical response. Whereas time-dependent density functional theory (TD-DFT) approach was used for excited state calculations of all the investigated chromophores (ETMMR and ETMM1–ETMM8). So, the influence of structural tailoring via end-capped acceptors modifications was explored by utilizing various quantum chemical analyses such as: transition density matrix (TDM), HOMO–LUMO band gap, density of states (DOS), UV–Vis, binding energy (Eb), global reactivity parameters (GRPs), molecular electrostatic potential (MEP) and open circuit voltage (Voc). Remarkably, all the derivatives (ETMM1–ETMM8) exhibited comparable results with that of the reference chromophore (ETMMR). The results of UV–Vis analysis in chloroform solvent fall in the following order for all the modified chromophores: ETMM5 > ETMM3 > ETMM8 > ETMM4 > ETMM7 > ETMM2 > ETMM6 > ETMM1, which demonstrated maximum red shift in ETMM5 (785.257 eV). Fascinatingly, lowest excitation energy (1.579 eV) as well as binding energy (0.319 eV) along with minimum HOMO/LUMO band gap (1.898 eV) suggested ETMM5 as an excellent candidate for high performance OSCs. Concludingly, all the results indicated that modification of end-capped acceptors is an effective alternative approach to obtain desirable optoelectronic properties.

Keywords

• Transition density matrix analysis
• Thiophene ring
• Reorganization energy
• Photovoltaic response
• A-π-A architecture