Exciton and Charge Carrier Interactions in Organic Solid State Films and the Device Application

已经认识到，使用磷光体的有机发光二极管（例如，Ir配合物）的电致发光（EL）效率显着下降（下一个），由于三重态-三重态激子湮灭在相当高的电流密度超过100 mA/cm ^2。除磷光材料外，荧光材料在高电流密度下也显示出EL效率的显著降低。本论文以一种典型的有机发光二极管结构α-NPD/Alq_3为研究对象，研究了电致发光器件中激子的湮灭过程。在J&lt;100 mA/cm ^2的电流密度下，我们观察到η_的变化<ext>与阴极结构有关。在有效电子注入的CsAl电极上，flext与电流密度无关，但随着电流的增加，flext逐渐增加，表明空穴和2电子的电荷注入平衡影响了η的波动<ext->。在高电流密度J&gt; 100 mA/cm^2时，flext随电流的增加急剧下降。我们将高电流密度下的湮没过程分为三类：单重态-单重态湮没（SSA）、单重态-极化子湮没（SPA）和单重态-热湮没（SHA）。

It has been recognized that organic light emitting diodes using phosphors (ex. Ir complexes) demonstrated significant decrease of electroluminescence (EL) efficiency (next) due to the triplet-triplet exciton annihilation at rather high current density over 100mA/cm^2. In addition to the phosphorescence materials, fluorescence materials also show significant decrease of EL efficiency at high current density. However, there are little studies on this subject.In this study, we clarify the exciton annihilation processes in electro-fluorescence devices using a typical OLED structure of α-NPD/Alq_3. At the current density of J<100mA/cm^2 we observed that change of η_<ext> is dependent on the cathode configuration. With efficient electron injection CsAl electrode, flext was independent of current density, whereas flext showed gradual increase with a current increase, suggesting that charge injection balance of hole and 2 electron influences the fluctuation of η_<ext-> Further, at high current density J>100mA/cm^2, flex steeply decreased with a current increase. We classified the annihilation processes at the high current density into three categories, singlet-singlet annihilation (SSA), singlet-polaron annihilation (SPA) and singlet-heat annihilation (SHA) models.