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Molecular‐level encapsulation of conjugated polymers serves as a potent approach to isolate the conjugated backbone for reducing intermolecular interactions and manipulating optoelectronic properties in solid state. Herein, by tuning the generation of dendritic carbazoles (Cz) in side chains, polydiarylfluorenes with efficient deep‐blue emission have been successfully synthesized and explored. The nonplanar twisted Cz dendrons endow their photoluminescence (PL) spectra with enhanced air‐aging stability and thermal stability owing to the formation of a self‐encapsulation layer. Their impact on solution‐state chain conformation and aggregation was thoroughly studied, combining small‐angle neutron scattering (SANS) and dynamic light scattering (DLS). Furthermore, benefiting from the suppressed intermolecular interactions, their films exhibit optimal behavior of singlet excitons in the excited state. Polymer light‐emitting diodes (PLEDs) adopting the spin‐coated and blade‐coated films both present comparable properties and stable electroluminescence (EL) spectra, with Commission Internationale de L'Eclairage (CIE) coordinates (x + y) < 0.3, demonstrating the feasibility of a self‐encapsulated molecular design strategy. Toward enhancing the spectral air‐aging stability of blue light‐emitting conjugated polymers in solution‐processed manufacturing, we proposed a design approach for molecular‐level encapsulation by introducing dendritic carbazoles (Cz) to the side chains. The unique nonplanar twisted Cz dendrons play critical roles in isolating conjugated backbones for reducing intermolecular interactions and manipulating their optoelectronic properties in the solid state.

Large‐area polymer light‐emitting diodes (PLEDs) manufactured by printing are required for flat‐panel lighting and displays. Nevertheless, it remains challenging to fabricate large‐area and stable deep‐blue PLEDs with narrowband emission due to the difficulties in precisely tuning film uniformity and obtaining single‐exciton emission. Herein, efficient and stable large‐area deep‐blue PLEDs with narrowband emission are prepared from encapsulated polydiarylfluorene. Encapsulated polydiarylfluorenes presented an efficient and stable deep‐blue emission (peak: 439 nm; full width at half maximum (FWHM): 39 nm) in the solid state due to their single‐chain emission behavior without inter‐backbone chain aggregation. Large‐area uniform blade‐coated films (16 cm2) are also fabricated with excellent smoothness and morphology. Benefitting from efficient emission and excellent printed capacity, the blade‐coated PLEDs with a device area of 9 mm2 realized uniform deep‐blue emission (FWHM: 38 nm; CIE: 0.153, 0.067), with a corresponding maximum external quantum efficiency and the brightness comparable to those of devices based on spin‐coated films. Finally, considering the essential role of deep‐blue LEDs, a preliminary patterned PLED array with a pixel size of 800 × 1000 µm2 and a monochrome display is fabricated, highlighting potential full‐color display applications. Large‐area blade‐coated deep‐blue polymer light‐emitting diodes (PLEDs) are fabricated based on encapsulated polydiarylfluorenes. Large‐area blade‐coated film presents a robust deep‐blue emission, associated with their intrachain singlet excitonic behavior. Large‐area deep‐blue PLEDs are obtained with a narrow‐band emission of FWHM ≈ 38 nm and a CIE of (0.153, 0.067), which are applied in the patterned pixel array and monochrome display.

Precisely optimizing the morphology of functional hybrid polymeric systems is crucial to improve its photophysical property and further extend their optoelectronic applications. The physic-chemical property of polymeric matrix in electrospinning (ES) processing is a key factor to dominate the condensed structure of these hybrid microstructures and further improve its functionality. Herein, we set a flexible poly(ethylene oxide) (PEO) as the matrix to obtain a series of polydiarylfluorenes (including PHDPF, PODPF and PNDPF) electrospun hybrid microfibers with a robust deep-blue emission. Significantly different from the rough morphology of their poly(N-vinylcarbazole) (PVK) ES hybrid fibers, polydiarylfluorenes/PEO ES fibers showed a smooth morphology and small size with a diameter of 1∼2 µm. Besides, there is a relatively weak phase separation under rapid solvent evaporation during the ES processing, associated with the hydrogen-bonded-assisted network of PEO in ES fibers. These relative “homogeneous” ES fibers present efficient deep-blue emission (PLQY>50%), due to weak interchain aggregation. More interestingly, low fraction of planar ( β ) conformation appears in the uniform PODPF/PEO ES fibers, induced by the external traction force in ES processing. Meanwhile, PNDPF/PEO ES fibers present a highest sensitivity than those of other ES fibers, associated with the smallest diameter and large surface area. Finally, compared to PODPF/PVK fibers and PODPF/PEO amorphous ES fibers, PODPF/PEO ES fibers obtained from DCE solution exhibit an excellent quenching behavior toward a saturated DNT vapor, mainly due to the synergistic effect of small size, weak separation, β -conformation formation and high deep-blue emission efficiency.