Designs And Syntheses Of Copolymers Based On Fluorene And Studies On Their Light-Emitting Properties

Polymer light-emitting diodes show much more potential application in flatpanel display, compared with organic molecule electroluminescent devices, and haveattracted much interests all over the world. In this dissertation, the development ofpolymer light-emitting materials and their devices is reviewed, especially forpolyfluorenes. To overcome the defects of polyfluorenes, four types of copolymerscontain squaric acid, maleimide, multiphenyl, triarylpyrazoline and 2-pyran-4-ylidene-malononitrile moieties based on fluorene were designed and synthesized,and were used to fabricate polymer light-emitting diodes. Their thermal stability,electrochemical property, photoluminescence, electroluminescence and therelationship between polymer structure and luminescent property were also studied. The research results indicated that polymers containing squaric acid, maleimideand 2-pyran-4-ylidene-malononitrile moieties have high electron affinity, and theirdevices can emit yellow and deep red light. The polymers containing multiphenylunits can effectively avoid to forming excimers, which is commonly observed inpolyfluorenes. So the introduction of multiphenyl units can improve the purity ofpolyfluorene's emitting light. On the other hand, polymers containingtriarylpyrazoline moieties have much higher photoluminescent andelectroluminescent quantum efficiencies. The toppest external quantum efficiencycan reach 2.5%. All of the copolymers are novel and prospective materials forapplication in polymer light-emitting diodes.