Ultrasmall magnetic field-effect and sign reversal in transistors based on donor/acceptor systems

Beilstein Journal of Nanotechnology

关键词: donor/acceptor system;    organic magnetoresistance;    organic transistors;    sign reversal;    ultrasmall magnetic field-effects;   

DOI  :  10.3762/bjnano.8.112

学科分类：地球科学(综合)

来源: Beilstein - Institut zur Foerderung der Chemischen Wissenschaften

【 摘 要 】

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-(N,N-di-p-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 B0 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.

【 授权许可】

CC BY