Device properties and degradation mechanisms of organic light-emitting diodes composed of organic layers with orientation polarization

本研究结果如下：1)有机半导体器件中常用的几种极性分子在其蒸发膜中自发形成取向极化。2)有机异质界面电荷的来源是取向极化产生的极化电荷。3)极性分子在有机异质界面附近的存在抑制了电荷的色散。4)极性分子成膜过程中的光照射改变了所合成器件中的电荷积累特性，从而缩短了器件的寿命。这些发现表明，永久偶极矩是影响有机半导体器件性能的重要参数。

Findings of this study are as follows : 1) Several polar molecules that are commonly used in organic semiconductor devices spontaneously forms orientation polarization in their evaporated films. 2) The origin of interface charge at organic hetero interfaces is polarization charge originating from the orientation polarization. 3) Presence of polar molecules in the vicinity of organic hetero interface suppresses charge dispersion. 4) Light irradiation during the film formation of a polar molecule changes the charge accumulation property in the resultant devices, and causes a shorter lifetime. These findings indicate that permanent dipole moment is an important parameter that strongly affects on the device properties of organic semiconductor devices.