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Strong Spin Orbital Coupling Effect On Magnetic Field Response Generated By Intermolecular Excited States In Organic Semiconductors, Liang Yan
Doctoral Dissertations
It has been found that non-magnetic organic semiconductors can show some magnetic responses in low magnetic field (<100 >mT). When applying magnetic field, the electroluminescence, electrical current, photocurrent, and photoluminescence could change with magnetic field, which are called magnetic field effects.
Magnetic field effects are generated through spin-dependent process affected by the internal magnetic interaction. In nonmagnetic materials, hyperfine interaction has been supposed to dominantly affect the spin-dependent process recently. But the conclusion was made in weak spin-orbital coupling organic semiconductor. The hyperfine interaction might not be the main reason responsible for magnetic field effects in strong spin-orbital coupling materials. …
Magnetic Field Dependent Electroluminescence And Charge Transport In Organic Semiconductors, Ming Shao
Magnetic Field Dependent Electroluminescence And Charge Transport In Organic Semiconductors, Ming Shao
Doctoral Dissertations
It has been found that a small magnetic field (<300 mT) can substantial change the electroluminescence, photoluminescence, photocurrent, electrical injection current in nonmagnetic organic semiconductors. It is generally believed that these magnetic field effects (MFE) are related to the spin dependent processes in organic semiconductor. However, the origin of MFE is still not well understood. In this dissertation, we investigate the underlying mechanism for magnetic field effects on electroluminescence (MFEEL) and magnetoresistance (MR) and demonstrate the complete tuning of MFEEL and MR based on our theoretical understanding.
We consider MFE arising from magnetic field sensitive intersystem crossing (ISC) and triplet charge reaction. Magnetic field can increase the singlet ratios through ISC, accounting for positive MFEEL. Magnetic field modulated ISC strongly depends on the electron-hole pair separation distance. MFE can be enhanced by increasing the electron hole pair distance through material mixing and interplaying the electric dipole-dipole interaction. Meanwhile, two possible mechanisms corresponding for negative MFEEL …