Self-encapsulated light-emitting conjugated polymers with enhanced spectra aging stability for deep-blue polymer light-emitting diodes

Abstract

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.

Keywords

carbazole dendrons / deep-blue polymer light-emitting diodes / light-emitting conjugated polymer / polydiarylfluorenes / self-encapsulation

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