Department of Electrical & Computer Engineering, and Waterloo Institute for Nanotechnology, University of Waterloo , 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada.
ACS Appl Mater Interfaces. 2013 Sep 11;5(17):8733-9. doi: 10.1021/am402537j. Epub 2013 Aug 23.
We study the stability of common hole transport material/electron transport material (HTM/ETM) interfaces present in typical organic light-emitting devices (OLEDs) under various stress scenarios. We determined that these interfaces degrade rapidly, because of an interaction between HTM positive polarons and HTM singlet excitons. The phenomenon results in a deterioration in conduction across the interface, and contributes to the commonly observed increase in OLED driving voltage with electrical driving time. This interfacial degradation can be slowed if the exciton lifetime becomes shorter. The findings uncover a new degradation mechanism that is interfacial in nature, which affects organic/organic interfaces in OLEDs and contributes to their limited electroluminescence stability, and shed light on approaches for reducing it. Although this study has focused on OLEDs, we can expect the same degradation mechanism to affect organic/organic interfaces in other organic optoelectronic devices where both excitons and polarons are present in high concentrations, such as in organic solar cells or photodetectors.
我们研究了在各种应力情况下，典型有机发光二极管（OLED）中常见的空穴传输材料/电子传输材料（HTM/ETM）界面的稳定性。我们发现，由于 HTM 正孔极化子和 HTM 单线态激子之间的相互作用，这些界面迅速降解。这种现象导致界面传导恶化，并导致通常观察到的 OLED 驱动电压随电驱动时间的增加而增加。如果激子寿命变短，这种界面降解可以减缓。研究结果揭示了一种新的界面退化机制，这种机制影响 OLED 中的有机/有机界面，并导致其有限的电致发光稳定性，为减少这种退化提供了思路。尽管本研究集中在 OLED 上，但我们可以预期，同样的降解机制也会影响其他有机光电设备中的有机/有机界面，这些设备中存在高浓度的激子和极化子，例如有机太阳能电池或光电探测器。
