Tuning the optoelectronic properties of triphenylamine (TPA) based small molecules by modifying central core for photovoltaic applications.

Small donor molecules based on fused ring acceptors exhibit encouraging photovoltaic properties and expeditious advancement in organic solar cells. Central core modification of non-fullerene acceptor materials is a favorable methodology to enhance electronic properties and efficiency for OSCs. Herein, four new donor molecules, namely, BDTM1, PYRM2, ANTM3, and NM4 are designed with a strong donor moiety triphenylamine, tetracyanobutadiene as acceptor unit, and thiophene as spacer linked to a modified central core. Geometric parameters, optical, electrical properties, effect of central core modification on tailored molecules BDTM1-NM4 are investigated and compared with reference DPPR. DFT together with TDDFT approaches using MPW1PW91 functional is used to study key parameters like absorption maximum (λmax), frontier molecular approach, ionization potential, electron affinity, the density of states, transition density matrix along with open-circuit voltage (VOC), dipole moment and reorganization energy. Among all these molecules, BDTM1 shows maximum calculated absorption λmax (817 nm) and the lowest band gap (2.54 eV). This bathochromic shift in BDTM1 is due to the presence of 4,8-dimethoxy-2,6-di-2-thienylbenzodithiophene as a strong electron-withdrawing group. Computed reorganization energies (RE) shows that BDTM1 has the highest hole and electron mobility among all designed molecules. Combination of BDTM1 donor and PC61BM acceptor further verifies charge transfer and their interaction. The results illustrate that designed donor molecules (BDTM1-NM4) are better in performance and are recommended for experimentation to develop efficient OSCs. Four new donor molecules, namely, BDTM1, PYRM2, ANTM3, and NM4 are designed with a strong donor moiety triphenylamine, tetracyanobutadiene as acceptor unit and thiophene as spacer linked to a modified central core. Geometric parameters, optical, electrical properties, effect of central core modification on tailored molecules BDTM1-NM4 are investigated and compared with reference DPPR.