Vapor Deposition Polymerization of an Oxadiazole Polymer and Its Application to Organic Light Emitting Diode

Abstract

Polymer thin films having oxiadiazole unit were prepared by the electron-assisted vapor deposition polymerization of its vinyl derivative (vPBD). Chemical analyses showed that the deposited film contained 60% of polymer component having molecular weight of several thousands. The result was applied for constructing an emissive layer (EML) of an organic light emitting diode (OLED). The EML was prepared by coevaporating vPBD with a vinyl derivative of an iridium complex (vIr(ppy)₃). The emission spectra suggested that the dopant units are copolymerized into the main chain of vPBD host polymer. Comparison was made with an EML that consisted of the standard oxadiazole host material (tBu-PBD) having no polymerizable functional group. The OLED having deposition-polymerized EML gave higher luminance compared to the device prepared without polymerization. Moreover, the device lifetime was improved as a consequence of deposition polymerization. The electron-assisted deposition of vinyl compounds can be an effective method to improve the device performance of OLEDs through the formation of stable polymer thin films, in which the dopant molecules are copolymerized uniformly.