Franco Leandro R, Marchiori Cleber, Araujo C Moyses
Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden.
Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden.
J Chem Phys. 2023 Nov 28;159(20). doi: 10.1063/5.0163180.
Non-fullerene electron acceptors have emerged as promising alternatives to traditional electron-acceptors in the active layers of organic photovoltaics. This is due to their tunable energy levels, optical response in the visible light spectrum, high electron mobility, and photochemical stability. In this study, the electronic properties of two representative non-fullerene acceptors, ITIC and Y5, have been calculated within the framework of density functional theory using a range of hybrid and non-hybrid density functionals. Screened range-separated hybrid (SRSH) approaches were also tested. The results are analyzed in light of the previously reported experimental outcomes. Specifically, we have calculated the oxidation and reduction potentials, fundamental and optical gaps, the highest occupied molecular orbital and lowest unoccupied molecular orbital energies, and exciton binding energies. Additionally, we have investigated the effects of the medium dielectric constant on these properties employing a universal implicit solvent model. It was found that hybrid functionals generally perform poorly in predicting oxidation potentials, while non-hybrid functionals tend to overestimate reduction potentials. The inclusion of a large Hartree-Fock contribution to the global or long range was identified as the source of inaccuracy for many hybrid functionals in predicting both redox potentials and the fundamental and optical gaps. Corroborating with the available literature, ∼50% of all tested functionals predicted very small exciton binding energies, within the range of ±0.1 eV, that become even smaller by increasing the dielectric constant of the material. Finally, the OHSE2PBE and tHCTHhyb functionals and the optimal tuning SRSH approach emerged as the best-performing methods, with good accuracy in the description of the electronic properties of interest.
非富勒烯电子受体已成为有机光伏活性层中传统电子受体的有前途的替代品。这是由于它们具有可调的能级、在可见光谱中的光学响应、高电子迁移率和光化学稳定性。在本研究中，使用一系列杂化和非杂化密度泛函，在密度泛函理论框架内计算了两种代表性非富勒烯受体ITIC和Y5的电子性质。还测试了筛选范围分离杂化（SRSH）方法。根据先前报道的实验结果对结果进行了分析。具体而言，我们计算了氧化和还原电位、基本能隙和光学能隙、最高占据分子轨道和最低未占据分子轨道能量以及激子结合能。此外，我们使用通用隐式溶剂模型研究了介质介电常数对这些性质的影响。发现杂化泛函在预测氧化电位方面通常表现不佳，而非杂化泛函往往高估还原电位。在预测氧化还原电位以及基本能隙和光学能隙时，许多杂化泛函不准确的根源被确定为对全局或长程包含了较大的哈特里-福克贡献。与现有文献一致，所有测试泛函中约50%预测的激子结合能非常小，在±0.1 eV范围内，并且随着材料介电常数的增加而变得更小。最后，OHSE2PBE和tHCTHhyb泛函以及最佳调谐SRSH方法成为表现最佳的方法，在描述感兴趣的电子性质方面具有良好的准确性。
