Synthesis And Properties Of Blue-light Emitting Polyfluorene Containing Functionalized Groups On The Side Chain

Polymer light-emitting diodes?PLEDs?have attracted widespread attention from academic and industry because of their wet-processing capability,high material utilization,low cost,and large-area displays.And they have great prospects for applications in full-colour flat-panel displays and solid-state lighting.In various polymer electroluminescent materials,the research of blue light-emitting polymers is particularly important,because it can not only provide blue light for solid-state lighting and full-color display,but also can convert blue light into green and red light through energy transfer.The development of a highly efficient and stable blue light-emitting polymers is crucial for achieving full color display of PLEDs.Polyfluorenes have emerged as the most promising blue light-emitting polymers because of their high solid-state photoluminescence quantum efficiency,easy chemical modification,good solubility and film formation.However,Polyfluorenes suffer from unexpected green emission after thermal annealing or upon long-term operation due to the formation of aggregation/excimer or ketone defects.As a result,polyfluorenes have lower electroluminescent efficiency and color purity,and limits its application in PLEDs.In order to overcome the disadvantages of polyfluorene,we introduced hole-transporting group into the polyspirofluorene,polysilafluorenes,and their copolymers side chain to balance the charge carriers fluxes;and we introduced the fluorescent dye group 2-?4-diphenylamine styryl?hydrazine?DPAS?into the polyfluorene side chain to achieve the energy transfer from the polyfluorene backbone to the fluorescent dye group,resulting in a stable and efficient electroluminescent.The main contents are as follows:1.We introduced the triphenylamine and carbazole groups with long alkyl chains into the polyspirofluorene and polysilafluorenes side chains to reduce the hole injection barrier and balance the injection and transport of the charage carrier fluxes.The single-layer device based on C₈TPA-PSF achieved a turn-on voltage of 2.7V,the maximum current efficiency of1.24cd/A with CIE coordinates of?0.17,0.09?,and the turn-on voltage is lower than sPF?3.3V?.The color coordinates of C₈TPA-PSF is very close to NTSC standard blue light with CIE coordinates?0.14,0.08?.C₈TPA-PSF is a good polymer blue light materials.2.We introduced narrow bandgap fluorescent dye 2-?4-diphenylaminostyryl?anthracene?DPAS?into the polyfluorene side chain to achieve an efficient F?rster energy transfer from polyfluorene backbone to side chain fluorescent dye moieties DPAS,and the device efficiency has significantly improved.From the photoluminescence spectra of the polymers P1,P2,P5,P6,P7,and P8 in different concentrations of chloroform solvents:the F?rster energy transfer from the polyfluorene backbone to the the fluorescent dye DPAS becomes more and more complete with the increase of the concentration.Compared to P0 without DPAS side chains,the maximum current efficiency of the device based on P1,P2,P7 and P8 with DPAS side chains are increased 8-10 times.