Correlation between exciton-induced degradation of organic/metal interfaces and energy barrier for electron injection at organic/metal interfaces in organic optoelectronic devices

摘要

We study exciton-induced degradation of various organic/metal interfaces in organic optoelectronic devices. The results show that organic/metal interfaces are susceptible to irradiation in general, resulting in a deterioration in charge transport across the interfaces. We find that organic/metal interfaces containing the same organic material but different metals degrade quite differently, where interfaces with metals of high work function are more susceptible to exciton-induced degradation than those with metals of low work function. The results suggest a clear correlation between excitoninduced degradation of organic/metal interfaces and energy barrier for electron injection at organic/metal interfaces. Furthermore, the fact that the use of interfacial layers, which usually contain alkali metals of extremely low work function, can greatly improve organic/metal interfacial photo-stability is also, to a large extent, consistent with such correlation. The reason behind such correlation may stem from the difference in the strength of organic-metal bonds in organometallic compounds formed at different organic/metal interfaces and/or the difference in band bending of organic materials in the vicinity of organic/metal interfaces due to the use of metals of different work functions at the interfaces.