# Electronic structure and non-linear optical properties of organic photovoltaic systems with potential applications on solar cell devices: A DFT approach

## TL;DR

This study uses DFT calculations to analyze the electronic and optical properties of 50 organic photovoltaic molecules, identifying promising candidates for solar cell applications with potential for improved light absorption and stability.

## Contribution

It provides a systematic DFT-based analysis of a large series of OPV materials, highlighting their stability, optical properties, and potential for photovoltaic use, aiding in in silico material design.

## Key findings

- Twisted geometries are most stable.
- All absorption spectra are red-shifted, enhancing visible light absorption.
- Identified candidate materials with suitable HOMO-LUMO gaps for solar cells.

## Abstract

The use of eco-friendly materials for the environment has been addressed as a critical issue in the development of systems for renewable energy applications. In this regard, the investigation of organic photovoltaic (OPV) molecules for the implementation in solar cells, has become a subject of intense research in the last years. The present work is a systematic study at the B3LYP level of theory performed for a series of 50 OPV materials. Full geometry optimizations revealed that those systems with a twisted geometry are the most energetically stable. Nuclear independent Chemical shifts (NICS) values show a strong aromatic character along the series, indicating a possible polymerization in solid-state, via a {\pi}-{\pi} stacking, which may be relevant in the design of a solar cell device. The absorption spectra in the series was also computed using Time Dependent DFT at the same level of theory, indicating that all spectra are red-shifted along the series. This is a promissory property that may be directly implemented in a photovoltaic material, since it is possible to absorb a larger range of visible light. The computed HOMO-LUMO gaps as a measurement of the band gap in semiconductors, show a reasonable agreement with those found in experiment, predicting candidate materials that may be directly used in photovoltaic applications. Non-linear optical (NLO) properties were also estimated with the aid of a PCBM molecule as a model of an acceptor, and a final set of optimal systems was identified as potential candidates to be implemented as photovoltaic materials. The methodological approach presented in this work may aid in the in silico assisted-design of OPV materials.