End-capped group modification on cyclopentadithiophene based non-fullerene small molecule acceptors for efficient organic solar cells; a DFT approach

• Published in: Journal of molecular graphics & modelling 2022-06, Vol.113, p.108162-108162, Article 108162
• Main Authors: Khan, Muhammad Imran, Iqbal, Javed, Akram, Sahar Javaid, El-Badry, Yaser A., Yaseen, Muhammad, Khera, Rasheed Ahmad
• Format: Article
• Language: English
• Subjects: Cyclopentadithiophene based molecules; Density functional theory; Molecular electrostatic potential; Power conversion efficiency; Transition density matrix
• ISSN: 1093-3263; 1873-4243
• DOI: 10.1016/j.jmgm.2022.108162

Four acceptor-donor-acceptor (A-D-A) type cyclopentadithiophene core-based non-fullerene small acceptor molecules were designed with the objective to improve the proficiency of photovoltaic cells. A comprehensive density functional theory (DFT) analysis was done by employing B3LYP functional with 6–31G(d,p) basis set to study optoelectronic properties of R as well as M1-M4 molecules, while the time-dependent self-consistent field (TDSCF) was utilized to analyze their excited state calculations. Several essential characteristics must be refined in order to enhance the efficiency of small molecular acceptors, i.e., the density of states (DOS), HOMO-LUMO band gap, transition density matrix (TDM), dipole moment, reorganization energy, light-harvesting efficiency, and open-circuit voltage, etc. In comparison to the R molecule, all the derived molecules show better maximum absorption (in chloroform solvent) with a range of 886–951 nm and a smaller band gap with a range of 1.65–1.55 eV M2 retains the least exciton binding energy of 0.24 eV, and amongst all the investigated molecules M3 molecule has the least interaction coefficient values so, it possesses better charge transport probability. The reorganization energy values in eV for both electron (0.00579) and hole (0.00737) are the least for M3 molecule, so this molecule exhibits better charge mobility for electron and hole. VOC of R and M1-M4 molecule was calculated by theoretically computing the values of their complexes with PTB7-Th donor molecule. Figure: The findings show that all of the compounds studied provide a significant contribution to the bathochromic shift of UV–visible absorption. With higher oscillator strength and light harvesting efficiency, all of the compounds studied had a smaller band gap. By blending all of the researched molecules (R, M1-M4) with a well-known donor molecule PTB7-Th, the open circuit voltage, fill factor, and power conversion of all of the investigated molecules (R, M1-M4) are examined. [Display omitted] ❖Four new cyclopentadithiphene based molecules (M1-M4) were designed.❖The optoelectronic properties of M1-M4 were compared with reference molecule.❖M1 provided the highest VOC amongst all.❖M1-M4 provided lower band gap and a bathochromic shift in λmax.❖Higher dipole moment of designed molecules provoked enhanced self-assembly in them.❖All the designed molecules exhibited lower excitation and binding energies than reference molecule.