Cross-linked luminescent films via electropolymerization of multifunctional precursors for highly efficient electroluminescence

Abstract

To fabricate stable organic light-emitting diodes, a cross-linked network that firmly fixes the position of the chromophore is an ideal structure, because quenching caused by aggregation and/or phase separation effects can be effectively restrained in such robust films. Herein, in situ electropolymerization (EP) of fluorene-based precursors containing multi-electroactive carbazole units (multi-functionality) is utilized to construct highly cross-linked, smooth and compact luminescent films for highly efficient and stable electroluminescent devices. Cyclic voltammetry (CV), UV and atomic force microscopy (AFM) studies of the series of precursors with varied functionality (2, 4 and 8) reveal that increasing the functionality of the EP precursor can significantly increase the deposition rate, cross-linking degree and packing density as well as the luminous efficiency and stability of the fabricated EP films. The electrode kinetic parameters, determined by CV and chronocoulometry (CC), indicate that such improvements in EP film properties could be attributed to the enhanced interfacial electron-transfer rate. These observations could potentially offer a new approach to adjust the microstructures of EP films and provide a simple way of enhancing the performance of organic luminescent devices.