Carrier transport is a critical aspect of organic optoelectronics. This study presents a comprehensive investigation of the ambipolar and anisotropic carrier transport properties and mechanisms in single crystals of the nonfullerene acceptor COi8DFIC. To achieve this, a lateral time-of-flight (TOF) technique was employed. COi8DFIC films with long-range ordered molecular packing were prepared, and the growth direction of the crystals was confirmed to be perpendicular to the crystal (11̅1̅) face. The in-plane carrier transport properties were then characterized in orientations parallel and perpendicular to the growth direction, revealing ambipolar transport in both orientations. By examining the correlation between drift mobility and temperature or electric field, we observed a Gaussian disorder model for hole transport, showcasing varying levels of energetic and positional disorder along the two orientations. Furthermore, we observed a variable range hopping model for electron transport with different hopping distances along the two orientations.

中文翻译：

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非富勒烯受体COi8DFIC单晶本征双极性和载流子传输机制的各向异性探讨

载流子传输是有机光电子学的一个重要方面。本研究对非富勒烯受体 COi8DFIC 单晶中的双极性和各向异性载流子传输特性和机制进行了全面研究。为了实现这一目标，采用了横向飞行时间（TOF）技术。制备了具有长程有序分子堆积的COi8DFIC薄膜，并证实晶体的生长方向垂直于晶体（11̅1̅）面。然后在平行和垂直于生长方向的方向上表征面内载流子传输特性，揭示了两个方向上的双极传输。通过检查漂移迁移率与温度或电场之间的相关性，我们观察到空穴传输的高斯无序模型，展示了沿两个方向的不同水平的能量和位置无序。此外，我们观察到电子传输的可变范围跳跃模型，沿两个方向具有不同的跳跃距离。