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

摘要

Electron injection plays a key role in electron–photon conversion properties ofinverted UV–visible organic light-emitting diodes (OLEDs). Herein, facilely preparedsolution-processed lithium carbonate (Li_2CO_3) formic acid and boric acidsolutions for tailoring electron injection in inverted near-UV (NUV) OLEDs arestudied. Superior film morphology and exceptional electronic properties of spincoatedLi_2CO_3 films are examined by atomic force microscopy, X-ray/ultravioletphotoelectron spectroscopy, current–voltage curves, and impedance spectroscopy.Efficient inverted NUV OLEDs are assembled using wide-bandgap moleculeof 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as emissive layer,showing maximum radiance of 5.24mWcm~(-2) (2.28mWcm~(-2)) and externalquantum efficiency of 2.47% (2.17%) with an optimal Li_2CO_3 formic acid of3mgml~(-1) (Li_2CO_3 boric acid of 7 mg ml~(-1)) as electron injection tailoring. TheNUV emission shows electroluminescence peaks of 404–406 nm and full width athalf maximum of 52–56 nm. The results provide some feasible approaches forenhancing the performance of organic electronic devices, which require strongelectron injection/extraction and accelerate industrialization.