Tuning the optoelectronic properties of Subphthalocyanine (SubPc) derivatives for photovoltaic applications

In the quest of enhanced power conversion efficiency (PCE) and device performance of small molecule based organic solar cells, four new acceptor-donor-acceptor (A-D-A) type novel chromophores (Y1-Y4) have been designed with subphthalocyanine (SubPc) as a common donor and different benzene bridged end-capped 2-methylenemalononitrile (A1), 6-methylene-2-thioxo-1,3-thiazinan-4-one (A2), 2-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1ylidene) malononitrile (A3) and 5-methylene-2-thioxothiazolidin-4-one (A4) acceptor groups. Photovoltaic and quantum chemical parameters of Yl-Y4 were computed through DFT and TD-SCF using selected B3LYP hybrid functional. Next, the parameters affecting chemical reactivity, opto-electronic properties, charge mobility and exciton dynamics of Y1-Y4 were characterized through calculations of frontier molecular orbitals, absorption profiles, density of states (DOS) and transition density matrix (TDM) respectively. The results imply that the designed candidates (Y1-Y4) proved more proficient in executing the afore-said parameters compared to R (reference). Amongst all, Y3 surpassed in exhibiting the best efficiency with highest absorption value (667 nm) and lowest band gap (2.12 eV). Moreover, low reorganization energies, high dipole moment and comparable values of open circuit voltage (Voc) make these molecules a useful tactic for use in small molecule based organic solar devices.