Theoretical Calculations of the Optical and Electronic Properties of Dithienosilole‐ and Dithiophene‐Based Donor Materials for Organic Solar Cells

Six Acceptor‐Donor‐Acceptor (A−D−A) types molecules with dimethyl dithieno[3, 2‐b:2′,3′‐d]silole)−2,6‐diyl (DTS) (M1‐M3) and dimethyl cyclopenta [2, 1‐b;3,4‐b]‐dithiophene (CPDT) (M4‐M6) core flanged by different acceptor units through methylthiophene bridge are evaluated as donor materials for photovoltaic applications. The photovoltaic properties of M1‐M3 and M4‐M6 are compared with standard RaRc and Rb,Rd respectively. Geometry optimization was performed with CAM−B3LYP/6‐31G (d) level of theory. TD‐CAM−B3LYP has been employed for the estimation of excited state properties of the molecules. M1, M2, M3 and M4, M5, M6 symbolized suitable frontier molecular orbital's (FMO's) energy levels with broad absorption spectra. The electron withdrawing substituents impart red shift in absorption spectra along with good consistancy of designed donor molecules. Reorganization energies of donor molecules (M1‐M6) showed ideal properties of charge mobility. M1 and M4 illustrated lowest λe values as compared to λh, thus dictated that designed donor molecules are of good choice for their electron donating ability. Furthermore, M2 and M6 demonstrated shortest Eg of 3.7 and 3.72 eV among HOMO and LUMO energy levels. Six Acceptor‐Donor‐Acceptor (A−D−A) type of molecules with dimethyl dithieno[3, 2‐b:2′,3′‐d]silole)−2,6‐diyl (DTS) (M1‐M3) and dimethyl cyclopenta [2, 1‐b;3,4‐b]‐dithiophene (CPDT) (M4‐M6) core flanged by different acceptor units through methylthiophene bridge are evaluated as donor materials for photovoltaic applications. The photovoltaic properties of M1‐M3 and M4‐M6 are compared with standard Ra, Rc and Rb, Rd respectively