Stoeckel Marc-Antoine, Olivier Yoann, Gobbi Marco, Dudenko Dmytro, Lemaur Vincent, Zbiri Mohamed, Guilbert Anne A Y, D'Avino Gabriele, Liscio Fabiola, Migliori Andrea, Ortolani Luca, Demitri Nicola, Jin Xin, Jeong Young-Gyun, Liscio Andrea, Nardi Marco-Vittorio, Pasquali Luca, Razzari Luca, Beljonne David, Samorì Paolo, Orgiu Emanuele
Université de Strasbourg, CNRS, ISIS UMR 7006, 8 allée Gaspard Monge, Strasbourg, 67000, France.
Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc, 20, Mons, B-7000, Belgium.
Adv Mater. 2021 Apr;33(13):e2007870. doi: 10.1002/adma.202007870. Epub 2021 Feb 25.
Charge transport in organic semiconductors is notoriously extremely sensitive to the presence of disorder, both internal and external (i.e., related to interactions with the dielectric layer), especially for n-type materials. Internal dynamic disorder stems from large thermal fluctuations both in intermolecular transfer integrals and (molecular) site energies in weakly interacting van der Waals solids and sources transient localization of the charge carriers. The molecular vibrations that drive transient localization typically operate at low-frequency (<a-few-hundred cm ), which makes it difficult to assess them experimentally. Hitherto, this has prevented the identification of clear molecular design rules to control and reduce dynamic disorder. In addition, the disorder can also be external, being controlled by the gate insulator dielectric properties. Here a comprehensive study of charge transport in two closely related n-type molecular organic semiconductors using a combination of temperature-dependent inelastic neutron scattering and photoelectron spectroscopy corroborated by electrical measurements, theory, and simulations is reported. Unambiguous evidence that ad hoc molecular design enables the electron charge carriers to be freed from both internal and external disorder to ultimately reach band-like electron transport is provided.
在有机半导体中，电荷传输对无序状态（包括内部无序和外部无序，即与介电层相互作用相关的无序）极为敏感，这一点众所周知，尤其是对于n型材料而言。内部动态无序源于弱相互作用范德华固体中分子间转移积分和（分子）位点能量的大幅热涨落，导致电荷载流子出现瞬态局域化。驱动瞬态局域化的分子振动通常在低频（<几百厘米）下运行，这使得通过实验评估它们变得困难。迄今为止，这阻碍了明确的分子设计规则的确定，以控制和减少动态无序。此外，无序也可能是外部的，由栅极绝缘体的介电特性控制。本文报道了一项对两种密切相关的n型分子有机半导体中电荷传输的综合研究，该研究结合了温度相关的非弹性中子散射和光电子能谱，并通过电学测量、理论和模拟进行了佐证。研究提供了明确的证据，表明特定的分子设计能使电子电荷载流子摆脱内部和外部无序，最终实现类能带电子传输。
