Electron spin resonance study of field-induced charge carriers in organic semiconductor devices

有机场效应器件作为世纪的低成本电子器件受到广泛关注。电子自旋共振（ESR）是一种直接研究自旋电荷载体性质的有力技术，它能直接揭示具有自旋的电荷载体的性质，从而反映出这些器件的功能。1.聚合物材料用ESR在具有最高电荷载流子迁移率的区域规则聚烷基噻吩的金属-绝缘体-半导体（MIS）二极管中发现了场致极化子信号。我们发现在较低的电荷浓度下自旋和电荷成正比，然而在较高的外加电压下，自旋密度出现饱和，这表明极化子向无自旋双极化子的转变。g值和线宽的角度依赖性表明了聚合物链在基底上的边对构型。然后根据理论计算了各向异性ESR谱，定量分析了角分布函数。 关于我们 极化子波函数分子材料并五苯薄膜（1cm ~ 2/Us）和红荧烯单晶（10 cm ~ 2/Us）具有最高的载流子迁移率。与东北大学岩佐教授小组合作，成功观察到并五苯场效应晶体管（FHIi）的场致ESR。谱线宽度反映了载流子在10个分子上的空间分布，表明了电子的带状输运。从g值和线宽来看，相对于衬底的π堆积分子构型对于高迁移率是优选的。在并五苯中，诱导自旋密度总是与载流子密度成正比，这与区域规则的聚烷基噻吩形成鲜明对比。关于红荧烯单晶，正在与大坂大学的竹谷教授和东北的岩佐教授小组进行合作。ESR信号的运动窄化是合理的，证明了红荧烯单晶的高迁移率Less

Organic field-effect devices attract much attention as low-cost electronic devices of the 21st century. Electron spin resonance (ESR) is a powerful technique in caner to clarify directly the properties of charge carders with spins, which manifest the functionalities of those devices.1.Polymeric materialsField-induced polaron signals are found by ESR in Metal-Insulator-Semiconductor (MIS) diodes of regioregular polyalkylthiophenes, the conducting polymer with the highest charge carrier mobility. We found the proportionality of spins and charges at lower charge concentration At higher applied voltages, however, the saturation of the spin density occurred, which indicates the transformation of the polarons to spinless bipolarons. The angular dependence of g-values and line widths indicate the edge-on configuration of the polymer chain onto the substrata Then the angular distribution function has been quantitatively analyzed by calculating the anisotropic ESR spectra based on the theoretic … More al polaron wave functions. We also succeeded in observing the ambipolar carriers in the composites with fullerene and its derivatives.2.Molecular materialsPentacene thin film (1cm2/Us) and rubrene single crystal (10cm2/Us) possess the highest charge carrier mobility among organic materials. Collaborated with Prof. Iwasa's group in Tohoku University, field-induced ESR of pentacene field-effect-transistors (FHIi) is successfully observed. The linewidth indicates the spatial extent of charge carrier over ten molecules, suggesting the band-like transport. From the g-value and linewidth, pi-stacking molecular configuration with respect to the substrate is hind to be preferable fm the high mobility. In pentacene, the induced spin density is always proportional to the carrier density in Clear contrast with the regioregular polyalkyhlvophenes. For the rubrene single crystal, collaboration with Prof. Takeya in Osaka University and Prof. Iwasa's group in Tohoku is underway. Motional narrowing of the ESR signals is Sound, demonstrating the high mobility of the rubrene single crystals Less