Predicting benzodithiophene based donor materials with enhanced 19.09% PCE, open-circuit voltage and optoelectronic attributes for solar cell applications: Photochemical insights from DFT

Abstract

Seven benzo[1,2-b:4,5-b′]dithiophene (BDT) based novel donor (D1-D7) molecules with A-π-D-π-A configuration are investigated by DFT and TD-DFT methods and a power conversion efficiency (PCE) of 19.09% is predicted for organic solar cells (OSCs). The fundamental core of these novel compounds is the BDT molecule (R), with other significant acceptors substituted on the outer borders. To study the geometrical, photovoltaic, and optoelectronic properties of the newly designed sensitizers (D1-D7), the CAM-B3LYP/6-31G(d,p) method was employed for computational analysis and comparison with BDT (R) Evaluations were conducted on open circuit voltage (Voc), power conversion efficiency (PCE), fill factor (FF), absorption spectra, the distribution pattern of electron density, charge mobility, electron, and hole reorganizational energy, the density of state (DOS), frontier molecular orbital (FMO), and transition density matrices (TDM)of the investigated compounds. In comparison to the reference compound (R), D2, D3, and D4 have better optical and chemical characteristics. The DOS plots and the FMOs analysis showed that the addition of acceptor groups finely improved the charge distribution in the molecules under study. The optoelectronic characteristics of the proposed structure D2 in chloroform solvent were the most improved, with a lower band gap (3.87 eV), higher maximum absorbance (533 nm), and lower binding energy (1.55 eV) than others investigated. The TDM graphs revealed the reliability of the charge transfer capability. In several molecules, the mobilities of charge transfer in designed compounds were equivalent to the reference R while the D2 was the lowest among all implying that the charge carriers would be more maneuverable. For all donors, the Voc was calculated with PC71BM. Voc is high for D2, D3, and D4, compared to R. All investigated compounds were predicted to have remarkable PCEs with high FF values. Especially, D2 has the higher Voc (2.422 V) and FF (94.12), which leads to the highest PCE of 19.09%. Hence, all calculated characteristics are very favorable to the potential of our designed molecules in photovoltaic applications.