高分子材料への電荷注入過程とその評価(II) : 高分子材料の電界発光

Abstract

1. Electroulminescence was observed in PET when an impulse voltage was applied. The electroluminescence depended on the electrode material of the cathode and showed only a weak temperature dependence and a superlinear dependence on the electric field. The spectrum of the electroluminescence was identical with that of the photoluminescence originating from PET molecules. Considering these results, the following mechanism was concluded to be responsible for the electroluminescence in PET. Electrons injected from the cathode by tunneling through the interfacial barrier are accelerated by the electric field to sufficiently high energy to excite or ionize PET molecules. They finally lose their energy and become trapped, forming a space charge layer. The electroluminescence occurs when the excited PET molecules are deactivated into their ground states. The generation and dissipation of the space charge is discussed in this paper, and analysis of the electroluminescence is shown to be useful for understanding the dynamic behavior of the space charge in polymers. 2. Electroluminescence in PET was also observed under AC voltages. The electroluminescence was found to be controlled by the injection of electrons from the Al electrode, together with the space charge accumulation. The occurrence of the injection and accumulation of electrons was demonstrated by thermally stimulated current analysis. The significant modification of the internal field by the space charge resulted in an asymmetrical waveform of the electroluminescence in each half-cycle of the AC voltage.