Zhang Tao, Concannon Nolan M, Holmes Russell J
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States.
ACS Appl Mater Interfaces. 2020 Jul 15;12(28):31677-31686. doi: 10.1021/acsami.0c07112. Epub 2020 Jul 6.
Charge-transfer (CT) states formed at organic donor-acceptor (D-A) semiconductor heterojunctions play a critical role in optoelectronic devices. While mobile, their migration has not been extensively characterized. In addition, the factors impacting the CT state diffusion length () have not been elucidated. Here, CT state is measured by using photoluminescence quenching for several D-A mixtures, with migration occurring along the bulk heterojunction. All D-A pairings considered yield a similar ∼ 5 nm in equal mixtures despite variations in the CT state energy and the constituent molecular structures. The CT state varies strongly with mixture composition and is well-correlated to the slowest charge carrier mobility, suggesting a direct method to tune CT state transport. These findings may be applied to elucidate the role of CT state migration in organic photovoltaic and light-emitting devices as well as to broadly explain the transport of interfacial excited states along inorganic and hybrid organic-inorganic heterojunctions.
在有机供体-受体（D-A）半导体异质结处形成的电荷转移（CT）态在光电器件中起着关键作用。虽然它们是可移动的，但其迁移尚未得到广泛的表征。此外，影响CT态扩散长度（）的因素也尚未阐明。在此，通过对几种D-A混合物使用光致发光猝灭来测量CT态，迁移沿着本体异质结发生。尽管CT态能量和组成分子结构存在差异，但所有考虑的D-A配对在等量混合物中产生的相似值约为5nm。CT态随混合物组成变化很大，并且与最慢的电荷载流子迁移率密切相关，这表明了一种调节CT态传输的直接方法。这些发现可用于阐明CT态迁移在有机光伏和发光器件中的作用，以及广泛解释界面激发态沿无机和有机-无机混合异质结的传输。
