Polymer-based organic light-emitting diodes (OLEDs) can be used to create solution-processed flexible, transparent and large area next-generation lighting and displays. OLEDs are cheaper, mercury free, more energy efficient than the current lighting and display technologies. The wide-scale adoption of this technology is hampered due to the very expensive fabrication costs of vacuum-deposited OLEDs, which are based on small molecule emitters. Polymer-based emitters offer an enticing alternative as the devices can be fabricated using cost-effective solution-processing techniques. What is presently required are polymer materials that show performance metrics comparable with their small molecule analogues.
In this proposed project, to realise 100% utilization of excitons in conventional fluorescent polymers, a series of TADF sensitized fluorescent emitting polyfluorenes are designed by introducing TADF pendant groups onto the conventional fluorescent polyfluorene emitter for low-cost mass production of highly efficient OLEDs. These TADF pendants with higher singlet energy level than that of polyfluorene backbone are expected to efficiently up-convert triplet excitons into singlet excitons, after which all generated singlet excitons will be transferred to polyfluorene backbone for efficient light emission. In addition, to avoid direct capture of triplet excitons by polyfluorene backbone, large volume steric pendants to surround the emissive polymer backbone will be incorporated. Moreover, the light emission spectra can be tuned by copolymerizing low bandgap monomers to cover the full colour range from blue to red. At last the energy transfer mechanism will be revealed by photophysics characterization. Thus, a novel design strategy for highly efficient and narrowly emissive TADF polymers is established.
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