Tuning the optoelectronic properties of cross conjugated small molecules using benzodithiophene as a core unit with favorable photovoltaic parameters: a DFT study

Abstract

In a recent study, cross conjugated molecules (BDT-C1 to BDT-C6) based on Benzo [1,2-b:4,5-b'] (BDT) as core units linked with different acceptor moieties are designed for encouraging photovoltaic applications. The optoelectronic study has been conducted by density functional theory (DFT) at B3LYP 6-31G (d, p) basis set combination by equating them with recently reported cross conjugated reference (BDT-CR) molecule and to study basic parameters such as frontier molecular orbital, the density of states, reorganization energy, maximum absorption, dipole moment, transition density matrix (TDM) and open-circuit voltage (V OC). Six new cross conjugated molecules (BDT-C1 to BDT-C6) with modified acceptor moieties are designed to evaluate their photophysical behavior in photovoltaic cells and the optoelectronic analysis of designed molecules indicates that among all cross conjugated molecules, BDT-C3 molecule exhibited the lowest bandgap value (1.84 eV) and broad absorption (747 nm) spectrum in dichloromethane due to extended conjugation in molecule than BDT-CR. TDM results reveal the easy dissociation of exciton due to the transfer of electron density in a diagonal direction from donor to acceptor moieties. The lowest value of electron mobility (0.0030 eV) and hole mobility (0.0027 eV) of BDT-C4 indicates its excellent electron and hole transfer behavior. The newly architecture molecule BDT-C1 displayed the highest V OC value of 1.52 eV concerning PC61BM. All above-mentioned outcomes reflect that our newly architecture cross conjugated molecules are suitable applicants for photovoltaic cells and can exhibit wonderful results in the quest of power conversion efficiency.