| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 95 === Fluorene-based conjugated polymers (PFs) have emerged as a very promising class of blue-light emitting materials for use in PLEDs because of their high thermal stability, high electroluminescence quantum efficiencies. However, one drawback has limited the application of polyfluorene in blue PLED. For example, excimer, aggregation and keto defect were observed and the formation of these interaction reduced PL and EL efficiency.
In this study, we prepared dendritic structure in side chain and branch unit in main chain to suppress long wavelength emission under annealing in thin films. Polyfluorene was named as PF. Linear with zero and one generation dendritic structures were named as PLG0 and PLG1, respectively. Hyperbranched with zero and one generation dendritic structures were named as PHG0 and PHG1. The thermal decomposition temperature (Td) of PF, PLG0, PLG1, PHG0 and PHG1 are 469, 402, 374, 413 and 377℃, respectively, and showed good thermal stability. Annealing studies under nitrogen were showed PHG1 couled suppressed long wavelength emission apparently. It proves dendritic group in side chain and branch unit in main chain to suppress aggregation or excimer formation. In electrochemical property of these polymers were investigated. One generation dendritic structure polymers could lower the HOMO energy level. In double layer LED device, the turn-on voltages were 4.7 V, 5.1 V, 5.2 V, 4.2 V and 4.4 V, and maximum luminance was 950 cd/m2, 390 cd/m2, 72 cd/m2, 2106 cd/m2 and 23 cd/m2. The EL spectra of all polyfluorene derivatives showed four emission peaks.
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