Organic conjugated molecules with a rigid rod‐like π‐backbone structure automatically and easily self‐assemble into an anisotropic nanostructure. However, supersecondary structures obtained from the hierarchical secondary self‐assembly of nanostructures have rarely been reported for non‐amphiphilic conjugated molecules. Here, a nanowire architecture as a supersecondary structure from an ultra‐deep‐blue fluorene‐based conjugated molecule (FCz‐C8‐Am) to improve the emission efficiency and stability is reported. In significant contrast to the four reference molecules, the FCz‐C8‐Am molecules grow into soft nanowires and further self‐assemble into a series of nanowire architectures in the gelation process. This is associated with the synergistic effect of the hydrogen bonds among the amide units, pendant π–π stacking interactions between pendant Cz units, and appropriate soft steric interaction among side‐chains, which are the three design requirements for preparing these nanowire architectures. Interestingly, this supersecondary architecture of FCz‐C8‐Am has a stable ultra‐deep‐blue emission, with an efficiency of ≈77% and a Commission Internationale de L'Eclairage (CIE) value of (0.16, 0.06) in the solid state. These findings provide a profound understanding of the relationship between the inherent molecular structure, supramolecular interaction, and supersecondary nano‐architecture, offering useful information for the development of new functional optoelectronic materials.

Intermolecular aggregation and phase transition are exacerbated by enhancing the free motion of small molecules in the solid state upon an external active stimulus, which is negative to the device performance and stability of deep-blue organic lightemitting diodes (OLEDs). Herein, we proposed a convenient and simple "flexible"-pendant-functionalization strategy to obtain a polystyrene (PS) derivative (PS-MC8TPA) with an excellent stable morphology and efficient deep-blue emission for polymer lightemitting diodes (PLEDs), compared to that of small molecular MC8TPA, even after thermal treatment at 180 °C in air. Meanwhile, the dense and flexible interchain entanglement not only can induce efficient dispersion of MC8TPA molecules in this polymeric system, endowing PS-MC8TPA with stable single-chromophore emission behavior without obvious intermolecular aggregation in the solid state, but also avoid the permeation of O 2 and H 2 O under thermal annealing and aging for 2 days to show a stable deepblue emission. More interestingly, significantly different from the device efficiency of MC8TPA that has a severe drop after thermal annealing, the device based on a PS-MC8TPA-annealed film presents a relatively high maximum current efficiency (CE: 1.15 cd/A), associated with a stable and efficient deep-blue emission (CIE: (0.18, 0.09)) of its annealed film. These abovementioned results confirmed the effectiveness of our flexible-pendant-functionalization strategy to prepare an efficient and a stable emitter for optoelectronic devices.

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Functional side chains of light-emitting conjugated polymers (LCPs) play critical roles in the photophysical, electronic, and mechanical performances of the solution-processed polymer light-emitting diodes (PLEDs). Herein, we reported a molecular design principle of polydiarylfluorenes for realizing pure-blue light emission that is introducing functional side chains containing carbazole and amide groups. Resulting from the steric hindrance effect of carbazole groups, the hydrogen bond interactions among the side-chain amide groups were destroyed. As a consequence, both solution-processed films and PLEDs based on such films presented pure-deep-blue emission with the Commission International de L’Eclairage (CIE) coordinates of (0.15, 0.10) and (0.17, 0.14), respectively. Time-resolved transient spectroscopy revealed their similar exciton behaviors in film excited states, and the ultrafast energy transfer occurred within tens of picoseconds. These insights enable us a deeper understanding about the influence of functional side chains on the optoelectronic properties and supply a feasible design strategy for high-performance conjugated polymers.

Green‐processable printed large‐area light‐emitting diode (LED) is the crucial component of the high quality solid lighting and flat‐panel display. Accelerating the replacement from fossil‐based solvents to sustainable ecofriendly solvent is desirable for solution‐based printed organic electronics. Herein, by simple introducing methyl to the benzene groups of polydiarylfluorene‐based polymer, this work realizes the solution processing of blue polymer light‐emitting diodes (PLEDs) with a bio‐based solvent of limonene toward large‐area printed display. Film processed from this solvent exhibits satisfactory morphology and remarkable photophysical performances, even though the polymer chains show more serious aggregation in solution. What's more, devices fabricated with spin‐coated films present higher external quantum efficiency (EQE) and better spectra repeatability. Encouraged by the good film‐forming ability of this polymer in limonene, this work realizes the fabrication of printed large‐area films (5 × 5 cm2) with uniform emission and surface morphology by blade coating. Furthermore, this work develops passive matrix (PM) PLEDs arrays with 20 × 20 pixels that can dynamically display monochrome letters and numbers, demonstrating the potential application of cost‐effective printing techniques in large‐area display.