Fluorene pendant-functionalization of poly(N-vinylcarbazole) as deep-blue fluorescent and host materials for polymer light-emitting diodes

π-Electron coupling of pendant conjugated segment in π-stacked semiconducting polymers always causes the formation of defect trapped sites and further quenched high-band excitons, which is harmful to the performance and stability of deep-blue polymer light-emitting diodes(PLEDs). Herein, considerate of “defect” carbazole(Cz) electromers in poly(N-vinylcarbazole)(PVK), a series of fluorene units are introduced into pendant segments(PVCz-DMe F, PVCz-FMe NPh and PVCz-DFMe NPh) to suppress the strongπ-electron coupling of pendant Cz units and enhance radiative transition toward fabricating sable PLEDs.Compared to PVCz-FMe NPh and PVCz-DFMe NPh, PVCz-DMe F spin-coated films show a relatively efficient deep-blue emission, completely similar to its single pendant chromophore, confirmed an extremely weak charge-transfer and electron coupling between adjacent pendant segments. Therefore, PLEDs based on PVCz-DMe F present stable and deep-blue emission with a high color purity(0.17, 0.08), associated with extremely weak defect emission at 600～700 nm(induced by carbazole electromers). Finally, PLEDs based on PVCz-DMe F/F8BT blended films(1:1) also present the high maximum luminance(Lmax) of 6261 cd/m2and current efficiency(CEmax) of 2.03 cd/A, confirmed slightly trapped sites formation. Therefore, precisely control the arrangement and packing model of pendant units in π-stacked polymer is an essential prerequisite for building efficient and stable emitter for optoelectronic devices.