Reichert Thomas, Saragi Tobat P I
Macromolecular Chemistry and Molecular Materials, Department of Mathematics and Science, Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany.
Accenture GmbH, Kaistraße 20, 40221 Düsseldorf, Germany.
Beilstein J Nanotechnol. 2017 May 19;8:1104-1114. doi: 10.3762/bjnano.8.112. eCollection 2017.
We present magnetoresistive organic field-effect transistors featuring ultrasmall magnetic field-effects as well as a sign reversal. The employed material systems are coevaporated thin films with different compositions consisting of the electron donor 2,2',7,7'-tetrakis-(,-di--methylphenylamino)-9,9'-spirobifluorene (Spiro-TTB) and the electron acceptor 1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile (HAT-CN). Intermolecular charge transfer between Spiro-TTB and HAT-CN results in a high intrinsic charge carrier density in the coevaporated films. This enhances the probability of bipolaron formation, which is the process responsible for magnetoresistance effects in our system. Thereby even ultrasmall magnetic fields as low as 0.7 mT can influence the resistance of the charge transport channel. Moreover, the magnetoresistance is drastically influenced by the drain voltage, resulting in a sign reversal. An average value of ≈2.1 mT is obtained for all mixing compositions, indicating that only one specific quasiparticle is responsible for the magnetoresistance effects. All magnetoresistance effects can be thoroughly clarified within the framework of the bipolaron model.
我们展示了具有超小磁场效应以及符号反转的磁阻有机场效应晶体管。所采用的材料体系是由电子给体2,2',7,7'-四（-二-甲基苯基氨基）-9,9'-螺二芴（Spiro-TTB）和电子受体1,4,5,8,9,12-六氮杂三亚苯六腈（HAT-CN）组成的不同成分的共蒸发薄膜。Spiro-TTB和HAT-CN之间的分子间电荷转移导致共蒸发薄膜中具有高本征电荷载流子密度。这增加了双极化子形成的概率，而双极化子形成是我们系统中磁阻效应的起因过程。由此，低至0.7 mT的超小磁场都能影响电荷传输通道的电阻。此外，磁阻受到漏极电压的显著影响，导致符号反转。所有混合成分的平均值约为2.1 mT，这表明只有一种特定的准粒子对磁阻效应负责。所有磁阻效应都可以在双极化子模型的框架内得到充分阐明。
