Synthesis And Luminescence Properties Of Bipolar Blue-emitting Polyfluorenes

Organic/polymer light-emitting diodes (O/PLEDs) exhibit wide application prospectin the fields of display and lighting for their excellent properties, such as low energyconsumption, autoluminescence, quick-response and wide view. Among the O/PLEDs,polyfluorenes (PFs) and their derivatives have been demonstrated as one of the mostimportant blue light-emitting polymer materials, not only for their high thermal stability,exceptionally high solution and solid-state fluorescence quantum yields, but also for theirgood processability and mechanical property. However, their applications were limited bythe intristic disadvantage of unbalanced transportion of electrons and holes.As a kind of electron withdrawing unit, dibenzothiophene-S,S-dioxide can effectivelyimprove electron injection and transportion capabilities. Fluorenes containingrich-electron triphenylamine and carbazole in lateral chain can improve the abilities ofhole injection and transportion. Therefore, the incorporation of SO and rich-electronfluorenes into polyfluorene backbone could balance the injection and transport of electronand hole, and then improve the efficiency of blue light-emitting polymers.Based on previous research results, polyfluorenes was optimized through theintroduction of electron-withdrawing and electron donating groups.In chapter2, bipolar blue polyfluorenes were synthesized by incorporation ofdibenzothiophene-S,S-dioxide and9,9-di(triphenylamine) fluorenes into backbones. Withthese polymers as light-emitting layers, devices with single-layer and double-layerstructures were fabricated， respectively. The single-layer-structure device based onPFT5SO15exhibited best electroluminescence efficiency, with the driving voltage,maximal luminous efficiency (LEmax), maximum external quantum efficiency (EQEmax),maximum luminance (Lmax) and CIE coordinates of3.7eV,7.1cd/A,5.6%,15097cd/m~2,(0.16,0.18), respectively.In chapter3, bipolar blue polyfluorenes were synthesized by incorporation ofdibenzothiophene-S,S-dioxide and9,9-di{4-[9-(6-hexyl) carbazole]phenyl}fluorenes.With these polymers as light-emitting layers, devices with single-layer and double-layer structures were fabricated, respectively. The double-layer-structure device based onPFCz10SO15exhibited best electroluminescence efficiency, with the driving voltage,maximal luminous effic iency (LEmax), maximum external quantum efficiency (EQEmax)and CIE coordinates of5.4eV,5.2cd/A,3.9%,(0.16,0.15), respectively.