Fujita Takatoshi, Noguchi Yoshifumi, Hoshi Takeo
Institute for Molecular Science, Okazaki, Aichi 444-0865, Japan.
Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University, Hamamatsu, Shizuoka 432-8561, Japan.
Materials (Basel). 2020 Jun 16;13(12):2728. doi: 10.3390/ma13122728.
Molecular orientations and interfacial morphologies have critical effects on the electronic states of donor/acceptor interfaces and thus on the performance of organic photovoltaic devices. In this study, we explore the energy levels and charge-transfer states at the organic donor/acceptor interfaces on the basis of the fragment-based GW and Bethe-Salpeter equation approach. The face-on and edge-on orientations of pentacene/C bilayer heterojunctions have employed as model systems. GW+Bethe-Salpeter equation calculations were performed for the local interface structures in the face-on and edge-on bilayer heterojunctions, which contain approximately 2000 atoms. Calculated energy levels and charge-transfer state absorption spectra are in reasonable agreements with those obtained from experimental measurements. We found that the dependence of the energy levels on interfacial morphology is predominantly determined by the electrostatic contribution of polarization energy, while the effects of induction contribution in the edge-on interface are similar to those in the face-on. Moreover, the delocalized charge-transfer states contribute to the main absorption peak in the edge-on interface, while the face-on interface features relatively localized charge-transfer states in the main absorption peak. The impact of the interfacial morphologies on the polarization and charge delocalization effects is analyzed in detail.
分子取向和界面形态对供体/受体界面的电子态有至关重要的影响，进而影响有机光伏器件的性能。在本研究中，我们基于基于片段的GW和贝塞耳-萨尔皮特方程方法，探索有机供体/受体界面处的能级和电荷转移态。并将并五苯/C双层异质结的面内和面外取向用作模型体系。对包含约2000个原子的面内和面外双层异质结中的局部界面结构进行了GW+贝塞耳-萨尔皮特方程计算。计算得到的能级和电荷转移态吸收光谱与实验测量结果合理吻合。我们发现，能级对界面形态的依赖性主要由极化能的静电贡献决定，而面外界面中诱导贡献的影响与面内类似。此外，离域的电荷转移态对面外界面的主要吸收峰有贡献，而面内界面在主要吸收峰处具有相对局域的电荷转移态。详细分析了界面形态对极化和电荷离域效应的影响。
