Azide-substituted Poly(N -ethyl-3-vinylcarbazole) as a Thermally Cross-Linkable Hole-Transporting Material for Polymeric Light-Emitting Diodes

We have successfully synthesized a series of thermally cross-linkable azide-substituted poly(N-ethyl-3-vinylcarbazoles) P1–P6. These polymers can be self-cross-linked by heat treatment under atmospheric conditions to form insoluble polymer matrices. Their electronic properties can be tuned by using various triphenylamine-substituted alkyne-based curing agents as additives. The polymeric materials can be simply coated on a substrate by spin coating or dip coating. Through the Huisgen 1,3-dipolar cycloaddition reaction, the polymeric film can be cured by alkyne-based curing agents effectively under copper-free conditions. This approach can be utilized in the fabrication of multilayer polymeric light-emitting devices (PLEDs). Under optimized conditions, we have demonstrated that the PLED of ITO/cured P5/PVK-Ir(ppy)3-t-PBD/Mg–Ag shows a turn-on voltage of 10.1 V (1 cd/m2), with the maximum brightness of 7851 cd/m2 and current efficiency of 12.8 cd/A.