The photophysics of platinum complexes and their application in organic light-emitting diodes.

摘要

An organic light emitting diode (OLED) is an electroluminescent device made by placing several organic thin films between two conductors. The materials that comprise films are the subject of intense investigation, and must be able to meet certain criteria for consideration of application. This dissertation describes the development of novel materials, their photophysical studies and application in OLEDs. The first chapter introduces how OLEDs work and how the materials affect device properties.The second chapter describes photophysical studies of an emitting material, FPt. Through quenching studies, it is found FPt undergoes self-quenching through excimer formation in solution at room temperature. The rate constants for monomer decay, excimer formation and decay were determined. Also the redox properties of FPt in both ground and excited state were obtained.The third chapter describes the synthesis and characterization of heavy metal (Platinum and Iridium) dyads based on the general formula C &andNM(O&and O)-(O&andO)MC&andN, where C&andN is a cyclometalating ligand and (O&andO)-(O&andO) is an ancillary beta-diketonate. Fundamental intramolecuar energy transfer was also studied in this dyads system. It shows that we can turn off the intramolecular energy transfer to realize dual emission for some dyads.Described in chapter 4 and 5, a novel color tuning of platinum complexes' emission is reported. A series of platinum binuclear complexes bridged by pyrazolate ligands were synthesized and characterized. The crystal structures show the Pt-Pt distance is controlled by the choice of the bridging ligands. Upon the decreasing of Pt-Pt distance, compounds exhibit different emissions i.e. blue, green and red, with the emitting state changing from a mixed 3LC/MLCT state to low-energy MMLCT state. Devices with these new compounds were fabricated and studied. Highly efficient Blue, Green Red and White OLEDs were achieved. The results show the molecular structure strongly affects material behavior in devices.The sixth chapter describes a new concept to manage singlet/triplet excitons in OLEDs, which allows for the potential of 100% IQE by using a blue fluorescent emitting material. New white OLEDs with the highest performance to date have been demonstrated applying this concept.