Electronic structure and nonlinear optical properties of organic photovoltaic systems with potential applications on solar cell devices: a DFT approach

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 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 values show a strong aromatic character along the series, indicating that a possible crystallization in solid-state may rise, via a pi-pi stacking. This may play a role in the design of a solar cell device. The absorption spectra in the series were also computed using time-dependent DFT at the same level of theory, indicating that all spectra are redshifted 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. Nonlinear optical properties were also estimated with the aid of a PCBM molecule as a model of an acceptor, and a final set of systems was identified with outstanding electronic structure properties related to the performance of solar cell materials. The methodological approach presented in this work may aid in the in silico-assisted design of OPV materials.