Designing of cyanobenzene based small molecules with suitable photovoltaic parameters for organic solar cells

In this research work, a theoretical analysis of the photovoltaic properties of nonfullerene organic solar cells is performed. Four molecules have been designed by incorporating different donor units around the central cyanobenzene based acceptor core through thiophene spacer by mimicking the structure of R. DFT and TD‐DFT have been used to explore the following properties of solar cell material: opto‐electronic properties, reorganization energy, transition density matrix, and open circuit voltage. The designed molecules have side groups triphenylamine (M1), 2‐(5‐(4 [diphenylamino]phenyl) thiophen‐2‐yl) acrylonitrile (M2), 4‐(5‐(ethynylthiophen‐2‐yl)‐N,N‐diphenylaniline (M3), and 4‐(benzo[c][1,2,5]thiadiazol‐4‐yl)‐N,N‐diphenylaniline (M4). Among all the designed molecules, M4 has shown bathochromic shift with λmax 663 nm due to extended conjugation between end‐capped donor units and central electron‐deficient core. Similarly, among all of the designed molecules M4 also shown lower mobility of electron (λe) and hole (λh) which are 0.0047 and 0.0050 eV, respectively, that are also comparable to R. The lower reorganization energy of M4 exhibits the higher transfer of charge among all other designed molecules. Moreover, the open circuit voltage of M4 was 1.56 eV according to that of PC61BM acceptor. Results showed that designed Acceptor‐π spacer‐Donor molecule opened a new pathway for the solar cell material with modified and advanced properties.