Synthesis and characterization of triple-azacrown ethers containing fluorene-cored derivatives: application as electron injection layer for significantly enhanced performance of PLEDs

Abstract

To enhance electroluminescence of polymer light-emitting diodes (PLEDs) using an environmentally stable aluminum cathode, we designed a novel water/alcohol-soluble electron injection material, FTC, composed of a fluorene core and triple azacrown ether terminals. FTC significantly enhances the emission performance of PLEDs [ITO/PEDOT:PSS/EML/EIL/Al] when used as the electron injection layer (EIL), especially in the presence of metal carbonates and metal acetates. The metal carbonate-doped devices showed the best performance due to their higher dissociation rate than metal acetates. In particular, the device using K₂CO₃ doped-FTC as the electron injection layer (EIL) exhibited significantly enhanced performance compared to the device without an EIL. For the device based on PF-Green-B as the emitting layer, the performance was significantly enhanced to 17 460 cd m⁻², 21.58 cd A⁻¹, and 12.42 lm W⁻¹, respectively, from 1220 cd m⁻², 0.72 cd A⁻¹, and 0.27 lm W⁻¹ for the non-FTC device. Using HY-PPV as the emitting layer, the device performance was also significantly enhanced to 10 990 cd m⁻², 6.93 cd A⁻¹, and 5.27 lm W⁻¹, respectively, from 680 cd m⁻², 0.07 cd A⁻¹, and 0.03 lm W⁻¹ for the non-EIL device. The results indicate that FTC with metal cations is an excellent electron injection candidate for the performance enhancement of PLEDs with a high work function Al cathode.