Computational and theoretical study of subphthalocyanine based derivatives by varying acceptors to increase the efficiency of organic solar cells

Abstract To enhance power conversion efficiency (PCE) of organic solar cells, four new small molecules were designed with subphthalocyanines (SubPc) as a common donor and different benzene bridged end-capped acceptor groups named as prop-1-yne (X1), 1,2,3,4,5-pentaflouro-6-methoxycyclohexane (X2), benzene-1,2,4,5-tetracarbonitrile (X3), and 1,2-diphenylethyne (X4). Photovoltaic effect and quantum parameters of X1-X4 were computed through DFT and TD-DFT by using a selected hybrid functional B3LYP at 6-31G (d, p). Opto-electronic properties such as, absorption maxima (λmax), band gap, charge mobilities and exciton dynamics of X1-X4 were characterized by analyzing the UV–Visible absorption spectra, frontier molecular orbitals (FMOs), reorganization energies and transition density matrix (TDM), respectively. The computed parameters of all the designed molecules were found to be more efficient than reference molecule R. Among all the designed molecules, the molecule X3 has highest absorption (λmax) at 562 nm, reduced band gap (2.07 eV), least reorganization energies of electrons (λe = 0.00462), hole (λh = 0.00232), better charge delocalization in Transition density matrix analysis, and maximum open-cicuit voltage (Voc) of 1.87 eV as compared with other molecules while least exciton binding energy is exhibited by X1 (0.295 eV). These results indicate that our designed molecules are promising donor materials in improving the device performance of OSCs.