Sun Wenbo, van der Heide Tammo, Vuong Van-Quan, Frauenheim Thomas, Sentef Michael A, Aradi Bálint, Lien-Medrano Carlos R
Institute for Theoretical Physics and Bremen Center for Computational Materials Science, University of Bremen, 28359 Bremen, Germany.
Institute for Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
J Chem Theory Comput. 2025 May 27;21(10):5103-5117. doi: 10.1021/acs.jctc.5c00232. Epub 2025 May 8.
Density functional tight binding (DFTB) is a quantum chemical simulation method based on an approximate density functional theory (DFT), known for its low computational cost and comparable accuracy to DFT. For several years, the application of DFTB in organic photovoltaics (OPV) has been limited by the absence of an appropriate set of parameters that adequately account for the relevant elements and necessary corrections. Here we have developed new parametrizations using hybrid functionals, including B3LYP and CAM-B3LYP, for OPV applications within the DFTB method in order to overcome the self-interaction error present in DFT functionals lacking long-range correction. These parametrizations encompass electronic and repulsive parameters for the elements H, C, N, O, F, S, and Cl. A Bayesian optimization approach was employed to optimize the free atom eigenenergies of unoccupied shells. The effectiveness of these new parametrizations was evaluated by a data set of 12 OPV donor and acceptor molecules, showing consistent performance when compared with their corresponding DFT references. Frontier molecular orbitals and optimized geometries were examined to evaluate the performance of the new parametrizations in predicting ground-state properties. Furthermore, the excited-state properties of monomers and dimers were investigated by means of real-time time-dependent DFTB (real-time TD-DFTB). The appearance of charge-transfer (CT) excitations in the dimers was observed, and the influence of alkyl side-chains on the photoinduced CT process was explored. This work paves the way for studying ground- and excited-state properties, including band alignments and CT mechanisms at donor-acceptor interfaces, in realistic OPV systems.
密度泛函紧束缚（DFTB）是一种基于近似密度泛函理论（DFT）的量子化学模拟方法，以其低计算成本和与DFT相当的精度而闻名。多年来，DFTB在有机光伏（OPV）中的应用一直受到缺乏一套适当参数的限制，这些参数无法充分考虑相关元素和必要的校正。在这里，我们开发了使用混合泛函（包括B3LYP和CAM-B3LYP）的新参数化方法，用于DFTB方法中的OPV应用，以克服缺乏长程校正的DFT泛函中存在的自相互作用误差。这些参数化涵盖了元素H、C、N、O、F、S和Cl的电子和排斥参数。采用贝叶斯优化方法来优化未占据壳层的自由原子本征能量。通过12个OPV供体和受体分子的数据集评估了这些新参数化的有效性，与相应的DFT参考文献相比，表现出一致的性能。研究了前线分子轨道和优化的几何结构，以评估新参数化在预测基态性质方面的性能。此外，通过实时含时DFTB（实时TD-DFTB）研究了单体和二聚体的激发态性质。观察到二聚体中电荷转移（CT）激发的出现，并探索了烷基侧链对光诱导CT过程的影响。这项工作为研究实际OPV系统中的基态和激发态性质，包括供体-受体界面处的能带排列和CT机制，铺平了道路。
