DFT study of electronic and optical properties of pentacene derivatives

Abstract

Context

This study analyzed the electronic and optical properties of pentacene derivatives chemically modified by adding nitro and amine groups at different positions on the molecular structure. The study aimed to understand the impact of these modifications on electronic and optical applications, focusing on improving performance in organic electronic devices and solar cells. The results showed that adding nitro groups as electron acceptors and amine groups as electron donors reduces the energy gap and increases the chemical activity of the molecules. It was also observed that changing the positions of these groups significantly affects the polar moment, reflecting changes in the charge distribution within the molecules. In terms of optical properties, the modified molecules showed high light absorption in the visible region of the electromagnetic spectrum, making them promising candidates for organic solar cell applications, where high light absorption efficiency is a prerequisite for these applications.

Methods

All calculations were performed using the Gaussian 09 software package. The study included molecular geometry optimization using density functional theory (DFT) with the B3LYP hybrid functional and 6-31G(d,p) basis set. Electronic properties, such as the highest occupied molecular orbital HOMO and lowest unoccupied molecular orbital LUMO energy levels, and the energy gap between them were calculated to evaluate the stability and chemical activity. Time-dependent density functional theory (TD-DFT) was used to analyze the optical properties and light absorption. In addition, fixed points were confirmed by vibrational frequency analysis to ensure that the optimized molecular structures represent stable states. The study also included a polar moment calculation to evaluate the effect of chemical modifications on the polarity of the molecules.