Computational DFT Study on Donor and Spacer Substitution in Arylamine-Based Push-Pull Molecules for Enhanced Photovoltaic Performance

Abstract

In this research, we will shed light on four simple molecules of the “push-pull" types (DPMA-T-DCV, DPMA-Se-DCV, MeCz-T-DCV and MeCz-Se-DCV) by investigating the impact of substituting the electron-donor block diphenylmethylamine (DPMA) by a N-methyl carbazol-3-yl group (MeCz) and replacing the thiophene π-spacer by a selenophene, while keeping the dicyanovinyl (DCV) group constant. These molecules are optimized by the DFT method at CAM-B3LYP functional level of the theory and 6-311G (d,p) basis set. Quantum chemical calculations show that these new compounds are suitable for use as electron donors in combination with acceptors such as phenyl-C61-butyric acid methyl ester (PCBM) in bulk-heterojunction solar cells for several reasons, including: i) all molecules present good optical properties and absorb in the visible zone between 507.03-587.72 nm, these values are almost similar to the experimental results 467-514 nm. ii) the energy gaps of the four investigated molecules range from 1.24 eV to 2.011 eV, which shows that all energy gaps are in good accordance with the condition to be used as a photovoltaic material. Additionally, our results indicate a significant increase in the energy gap (0.30 eV) when substituting DPMA by MeCz in the thiophene series, aligning well with experimental observations (approximately 0.27 eV).