Solution-Processed OLED Based on a Mixed-Ligand Europium Complex

Abstract

An approach to increase the efficiency of europium-based OLEDs was proposed through the formation of a mixed-ligand complex. The design of a series of europium complexes, together with an optimization of the solution deposition, including the host selection, as well as the variation of the solvent and deposition parameters, resulted in a noticeable increase in OLED luminance. As a result, the maximum luminance of the Eu-based OLED reached up to 700 cd/m2, which is one of the highest values for an Eu-based solution-processed OLED. Finally, its stability was investigated.

First Dual Red–Near-Infrared Emissive Solution-Processed Organic Light-Emitting Diode Based on Europium–Ytterbium Mixed-Ligand Complexes for Pulse Oximetry

“…Complexes Eu x Yb 1– x (dbm) 3 BPhen were tested in solution-processed OLEDs with heterostructure ITO/PEDOT/PSS/poly-TPD/EML ≡ Eu x Yb 1– x (dbm) 3 BPhen/CBP/TPBi/LiF/Al (Table ). In order to increase the OLED efficiency, the host material CBP with high ambipolar charge mobility, which is known as the best host for solution-processed lanthanide-based OLEDs, was introduced. − Due to the high charge carrier mobility of chosen ligands, the obtained complexes OLEDs A–D demonstrated high current densities (Figure b). …”

The increase of europium-based OLED luminance through reducing the excited state lifetime by mixed-ligand complex formation

“…We selected CBP as a host material in EML due to: (1) its high HOMO level (5.9 eV) and high excited state energy (2.6 eV), suitable to cause efficient energy transfer to europium luminescence, 38 (2) it is an ambipolar host, 39 and (3) it is known as the best host for solution-processed OLEDs. 40 The doping concentration (25 wt%) was selected based on our previous study. 17 All the obtained OLEDs demonstrated solely typical intense electroluminescence spectra of europium ions (Fig.…”