LeCroy Garrett, Ghosh Raja, Sommerville Parker, Burke Colm, Makki Hesam, Rozylowicz Kalee, Cheng Christina, Weber Mark, Khelifi Wissem, Stingelin Natalie, Troisi Alessandro, Luscombe Christine, Spano Frank C, Salleo Alberto
Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States.
J Am Chem Soc. 2024 Aug 7;146(31):21778-21790. doi: 10.1021/jacs.4c06006. Epub 2024 Jul 26.
In this work, we compare two structurally near-amorphous rigid-rod polymers─poly(indacenodithiophene--benzothiadiazole), p(IDT-BT), and poly(indacenodithiophene--benzopyrollodione), p(IDT-BPD)─with orders of magnitude different mobilities to understand the effect charge carrier intrachain delocalization has on electronic transport. Quantum chemical calculations show that p(IDT-BPD) has a barrier to torsion that is significantly lower than that of p(IDT-BT) and is thus more likely to have reduced conjugation lengths. We utilize absorption and photoluminescence spectroscopy to characterize energetic disorder and show that p(IDT-BPD) has higher energetic disorder. Charge modulation spectroscopy (CMS) and model calculations are used to show that charge carriers are substantially delocalized in p(IDT-BT) and occupy near-uniform energetic environments. We find that mobility activated hopping barriers are similar in these two materials. Electronic structure calculations show that both intrachain and interchain couplings of monomer units are poor enough in p(IDT-BPD) that charge carriers collapse to single IDT units and transport via a through-space tunneling mechanism. This work highlights the remarkable charge transport properties of p(IDT-BT) by showing that high mobilities are achievable on device-relevant length scales with only 1D carrier delocalization.
在这项工作中，我们比较了两种结构上近乎非晶态的刚性棒状聚合物——聚（茚并二噻吩 - 苯并噻二唑），p(IDT - BT)，和聚（茚并二噻吩 - 苯并吡咯二酮），p(IDT - BPD)——它们的迁移率相差几个数量级，以了解电荷载流子链内离域对电子传输的影响。量子化学计算表明，p(IDT - BPD)的扭转势垒明显低于p(IDT - BT)，因此更有可能具有缩短的共轭长度。我们利用吸收光谱和光致发光光谱来表征能量无序，并表明p(IDT - BPD)具有更高的能量无序。电荷调制光谱（CMS）和模型计算用于表明电荷载流子在p(IDT - BT)中基本离域，并占据近乎均匀的能量环境。我们发现这两种材料中的迁移率激活跳跃势垒相似。电子结构计算表明，在p(IDT - BPD)中，单体单元的链内和链间耦合都很差，以至于电荷载流子坍缩到单个IDT单元，并通过空间隧道机制传输。这项工作通过表明仅通过一维载流子离域就能在与器件相关的长度尺度上实现高迁移率，突出了p(IDT - BT)卓越的电荷传输特性。
