There Is The Stability Of Organic Electroluminescent Devices Studied

Since the demonstration of the first double-layer organic electroluminescent device in 1987, more and more researchers have paid attention to organic light-emitting devices (OLEDs) due to their potential application in flat-panel displays. Although OLEDs have shown sufficient brightness and range of color, some other issues remain critical for practical applications. One such issue is the stability of OLEDs. We focus on the unstable infector coming from the structure of OLEDs. It contains the following works and innovations:1. Reliability is still the primary issue of industrial research on OLEDs. One cause of degradation of the evaporated devices has been clearly identified: the lack of reliability of the organic-inorganic contacts. We have found that by adding a flexible NaSt buffer layer of suitable thickness between the Alq₃ layer and A1 cathode in OLEDs, the thermal stability is significantly improved, as well as the current injection efficiency and electroluminescence output. This flexible connection between organic and inorganic should be of benefit to industry application of the OLEDs.2. Symmetric doped OLEDs have been used to study the mechanism of the current dependence of emission spectra. With the increasing current, the emission of dopants in the doped devices drops more steeply than that from the host. It is derived that the amount of dopant molecules with trapped electrons increases linearly with applied voltage. The spectral evolution of doped OLED is attributed to changing amount of dopant molecules with trapped electrons which block energy transfer from the host molecules. Because the EL and PL emissions from dopants both come mainly from energy transfer, the mechanism of PL spectral evolution could also apply to the EL spectral evolution.