title: Spin radical enhanced magnetocapacitance effect in intermolecular excited states.
abstract: This article reports the magnetocapacitance effect (MFC) based on both pristine polymer MEH-PPV and its composite system doped with spin radicals (6R-BDTSCSB). We observed that a photoexcitation leads to a significant positive MFC in the pristine MEH-PPV. Moreover, we found that a low doping of spin radicals in polymer MEH-PPV causes a significant change on the MFC signal: an amplitude increase and a line-shape narrowing under light illumination at room temperature. However, no MFC signal was observed under dark conditions in either the pristine MEH-PPV or the radical-doped MEH-PPV. Furthermore, the magnitude increase and line-shape narrowing caused by the doped spin radicals are very similar to the phenomena induced by increasing the photoexcitation intensity. Our studies suggest that the MFC is essentially originated from the intermolecular excited states, namely, intermolecular electron-hole pairs, generated by a photoexcitation in the MEH-PPV. More importantly, by comparing the effects of spin radicals and electrically polar molecules on the MFC magnitude and line shape, we concluded that the doped spin radicals can have the spin interaction with intermolecular excited states and consequently affect the internal spin-exchange interaction within intermolecular excited states in the development of MFC. Clearly, our experimental results indicate that dispersing spin radicals forms a convenient method to enhance the magnetocapacitance effect in organic semiconducting materials.
authors.affiliation: Department of Materials Science and Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: Huidong
authors.initials: H
authors.lastname: Zang
authors.forename: Jianguo
authors.initials: J
authors.lastname: Wang
authors.forename: Mingxing
authors.initials: M
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: He
authors.forename: Zitong
authors.initials: Z
authors.lastname: Liu
authors.forename: Deqing
authors.initials: D
authors.lastname: Zhang
authors.forename: Bin
authors.initials: B
authors.lastname: Hu