Studies On Magnetic Field Effects In Organic Semiconductor Devices

The recent discovery of magnetic field effect in organic devices has caused a world-wide interest in the past few years. Compared with traditional spin devices, organic field effect devices do not contain any ferromagnetic materials, which means it is difficult to use any of the well-established theoretical models to explain this intriguing phenomenon. And the intrinsic properties of organic materials, such as strong spin coherence, flexibility and low cost, make the effect a potential stock with a great scientific importance and wide applications.In this paper we studied the magnetic field effect in organic solar cells and organic light-emitting diodes. By using optoelectronic, spectroscopic and morphological methods, we illustrate some particular behaviors of the magnetic field effect in devices of different conditions. We attempt to explain the internal mechanism with the theories in the earlier studies. The main results of this paper are as follows:1) We prepared organic solar cell and organic light-emitting devices by the methods of spin coating and thermal evaporation, and investigated the optoelectronic properties, spectral response, and surface morphology of the devices.2) The organic solar cells with different D/A ratio, thickness of active layer and annealing treatment were prepared, and tested with their IV characteristics, absorption/PL spectra and surface morphology. Then we tested the magnetic field effects on these devices. The results showed that the exciton recombination rate is a key factor to organic magnetic field effect.3) We fabricated organic light-emitting devices with active layer of Alq3and MEH-PPV. The studies on the magnetic field effect of the organic emitting diodes showed that this effect is greatly influenced by the non-equilibrium injection of the devices.