Experimental Physics II and Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany.
J Am Chem Soc. 2013 Feb 6;135(5):1772-82. doi: 10.1021/ja308820j. Epub 2013 Jan 29.
In order to unravel the intricate interplay between disorder effects, molecular reorganization, and charge carrier localization, a comprehensive study was conducted on hole transport in a series of conjugated alternating phenanthrene indenofluorene copolymers. Each polymer in the series contained one further comonomer comprising monoamines, diamines, or amine-free structures, whose influence on the electronic, optical, and charge transport properties was studied. The series covered a wide range of highest occupied molecular orbital (HOMO) energies as determined by cyclovoltammetry. The mobility, inferred from time-of-flight (ToF) experiments as a function of temperature and electric field, was found to depend exponentially on the HOMO energy. Since possible origins for this effect include energetic disorder, polaronic effects, and wave function localization, the relevant parameters were determined using a range of methods. Disorder and molecular reorganization were established first by an analysis of absorption and emission measurements and second by an analysis of the ToF measurements. In addition, density functional theory calculations were carried out to determine how localized or delocalized holes on a polymer chain are and to compare calculated reorganization energies with those that have been inferred from optical spectra. In summary, we conclude that molecular reorganization has little effect on the hole mobility in this system while both disorder effects and hole localization in systems with low-lying HOMOs are predominant. In particular, as the energetic disorder is comparable for the copolymers, the absolute value of the hole mobility at room temperature is determined by the hole localization associated with the triarylamine moieties.
为了揭示无序效应、分子重组和电荷载流子局域化之间错综复杂的相互作用，我们对一系列共轭交替菲并二茚共聚体中的空穴传输进行了综合研究。该系列中的每个聚合物都包含一个额外的共聚单体，包括单胺、二胺或无胺结构，研究了它们对电子、光学和电荷输运性质的影响。该系列涵盖了通过循环伏安法测定的最高占据分子轨道（HOMO）能量的广泛范围。根据飞行时间（ToF）实验作为温度和电场函数推断出的迁移率发现与 HOMO 能量呈指数关系。由于这种效应的可能起源包括能量无序、极化子效应和波函数局域化，因此使用各种方法确定了相关参数。首先通过对吸收和发射测量的分析以及其次通过对 ToF 测量的分析来确定无序和分子重组。此外，还进行了密度泛函理论计算，以确定聚合物链上的空穴是局域化还是离域化的，并将计算出的重组能与从光学光谱推断出的重组能进行比较。总之，我们得出结论，在该体系中，分子重组对空穴迁移率影响很小，而低 HOMO 体系中的无序效应和空穴局域化都占主导地位。特别是，由于共聚体的能量无序相当，室温下空穴迁移率的绝对值取决于与三芳基胺部分相关的空穴局域化。
