Jin Qianqian, Xu Tao, Wang Changwei, Yin Shiwei
School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China.
Hubei Key Laboratory of Processing and Application of Catalytic Materials, College of Chemistry and Chemical Engineering, Huanggang Normal University, Huanggang 438000, China.
J Phys Chem A. 2025 Jul 3;129(26):5911-5919. doi: 10.1021/acs.jpca.5c03435. Epub 2025 Jun 18.
Accurate modeling of charge carrier energetics in organic semiconductors is essential for understanding and optimizing their performance in optoelectronic devices. In this work, we employ the absolutely localized molecular orbital (ALMO) method within density functional theory (DFT) as a quantum mechanical benchmark to evaluate the performance of isotropic (ISO) and anisotropic (ANISO) polarization models implemented in the AMOEBA polarizable force field (PFF). By analyzing a set of representative p-type and n-type organic semiconductors in both bulk-like (center-site) and surface-like (edge-site) cluster configurations, we assess the ability of each model to reproduce ALMO-based apparent polarization energies. Our results show that both ISO and ANISO models yield comparable accuracy in centrosymmetric (bulk-like) environments due to the suppression of anisotropic polarization effects. However, the ANISO model significantly outperforms the ISO model in asymmetric configurations, such as at molecular surfaces or heterojunction interfaces, where direction-dependent polarization becomes non-negligible. ALMO-based energy decomposition analysis (ALMO-EDA) reveals that polarization interactions are the dominant contribution to the transport gap in the condensed phase. This finding provides a simplified theoretical framework for estimating the transport gap by considering only polarization effects. Overall, this study establishes the reliability of the ALMO method as a reference for evaluating polarization models and highlights the importance of incorporating anisotropic polarizability in force fields for accurate modeling of charge localization and transport phenomena in organic materials.
准确模拟有机半导体中的电荷载流子能量对于理解和优化其在光电器件中的性能至关重要。在这项工作中，我们采用密度泛函理论（DFT）中的绝对定域分子轨道（ALMO）方法作为量子力学基准，来评估在AMOEBA可极化力场（PFF）中实现的各向同性（ISO）和各向异性（ANISO）极化模型的性能。通过分析一组具有代表性的p型和n型有机半导体在块状（中心位点）和表面状（边缘位点）簇构型中的情况，我们评估了每个模型再现基于ALMO的表观极化能量的能力。我们的结果表明，由于各向异性极化效应的抑制，ISO和ANISO模型在中心对称（块状）环境中产生的精度相当。然而，在不对称构型中，如在分子表面或异质结界面，方向依赖性极化变得不可忽略，ANISO模型明显优于ISO模型。基于ALMO的能量分解分析（ALMO-EDA）表明，极化相互作用是凝聚相中传输能隙的主要贡献。这一发现提供了一个简化的理论框架，通过仅考虑极化效应来估计传输能隙。总体而言，本研究确立了ALMO方法作为评估极化模型参考的可靠性，并强调了在力场中纳入各向异性极化率对于准确模拟有机材料中的电荷定位和传输现象的重要性。
