Surface Plasmon-based Red-emission Organic Light-emitting Diodes

Organic light-emitting diode(OLED) has a potential and wide application prospect in panel displays and solid lighting due to its high brightness, fast response, high efficiency, low energy consumption, flexible, low cost, and so on. Luminous efficiency and lifetime need to be improved in order to promote the industrialization process of OLED.Recently, surface plasmon(SP) has attracted much attention since it can enhance electroluminescent(EL) intensity in OLEDs. Localized surface plasmon(LSP) generated by discrete metal nanoparticles has been intensively investigated due to a simple manufacture process, easy control and low costs of the metal nanoparticles or nanoclusters. The metal nanoparticles are often located in an electron transporting layer(ETL) after an emitting layer(EML) or in a hole transport layer(HTL) before the EML, even directly deposited under the reflective cathode. According to previous reports, incorporating metal nanoparticles into the HTL have efficiently enhanced or significantly decreased OLED performances. In this thesis, some research work has been done on surface plasmon OLEDs with as-synthesized metal nanoparticles.The influence of Au nanoparticles on electrical and EL performances in OLEDs via spincoating as-synthesized Au nanorods(NRs) or nanocubes(NCs) onto a hole-injection layer(HIL) has been intensively investigated. Through accurately controlling the distance between the Au NRs and the EML, altering the guest emitter’s lifetime, and replacing Au NRs with Au NCs to satisfy a better spectra overlap with the emission guest, we demonstrated that it doesn’t generate any coupling between Au NRs and a red phosphor Ir(MDQ)2(acac) and in constrast, it exists coupling between Au NRs/NCs and a red fluorophore DCJTB. Although the coupling efficiently enhance the spontaneous raditive rate of DCJTB, it doesn’t improve the OLED performance, suggesting the increase in performance may originate from many factors, including but not limited to the incease in spontaneous raditive rate although it is considered as the only influence factor in previous literatures. Related research work is still going on.