Facilely Solution‐Processed Lithium Carbonate for Tailoring Electron Injection in High‐Performance Inverted Near‐UV Organic Light‐Emitting Diodes

Abstract

Electron injection plays a key role in electron–photon conversion properties of inverted UV–visible organic light‐emitting diodes (OLEDs). Herein, facilely prepared solution‐processed lithium carbonate (Li2CO3) formic acid and boric acid solutions for tailoring electron injection in inverted near‐UV (NUV) OLEDs are studied. Superior film morphology and exceptional electronic properties of spin‐coated Li2CO3 films are examined by atomic force microscopy, X‐ray/ultraviolet photoelectron spectroscopy, current–voltage curves, and impedance spectroscopy. Efficient inverted NUV OLEDs are assembled using wide‐bandgap molecule of 2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole as emissive layer, showing maximum radiance of 5.24 mW cm−2 (2.28 mW cm−2) and external quantum efficiency of 2.47% (2.17%) with an optimal Li2CO3 formic acid of 3 mg ml−1 (Li2CO3 boric acid of 7 mg ml−1) as electron injection tailoring. The NUV emission shows electroluminescence peaks of 404–406 nm and full width at half maximum of 52–56 nm. The results provide some feasible approaches for enhancing the performance of organic electronic devices, which require strong electron injection/extraction and accelerate industrialization.