Multiphosphine‐Oxide Hosts for Ultralow‐Voltage‐Driven True‐Blue Thermally Activated Delayed Fluorescence Diodes with External Quantum Efficiency beyond 20%

Abstract

Highly efficient low-voltage-driven -true-blue thermally activated -delayed fluorescence diodes are realized through employing a tri-phosphine oxide host (2,2',4-tris(di(phenyl) -phosphoryl)-diphenylether (DPETPO)) with a record external quantum efficiency of 23.0% and the lowest onset voltage of 2.8 V to date.

Dual n-type units including pyridine and diphenylphosphine oxide: effective design strategy of host materials for high-performance organic light-emitting diodes

“…Secondly, as indicated by the higher electron currents in electron-only devices (Fig. 5), p -PyPOmCP and m -PyPOmCP possess higher electron mobilities than PymCP due to the additional incorporation of the electron-transporting DPPO group, 25 which definitely facilitates electron transport and a better balance of holes and electrons within the emitting layer, and finally is favorable for higher emission efficiencies. The enhanced electron mobility in these DPPO-containing hosts can also be verified by the variation of the EL spectra of these blue devices.…”

Isomeric Thermally Activated Delayed Fluorescence Emitters for Color Purity-Improved Emission in Organic Light-Emitting Devices

“…32 Thus, it is impossible to realize high efficiencies in OLED displays with current TADF emitters. 17,[29][30][31][32] Most recently, Hatakeyama and his co-workers successfully utilized the multiple resonance effect to construct TADF emitters with extremely narrow FWHM. 32 However, this strategy is strictly confined to specific molecular structure and inapplicable for current D-A structure TADF emitters; and the OLEDs based on their new TADF emitters suffer serious efficiency roll-off and extremely low maximum luminance of about 200 cd m -2 .…”

Tailoring Optoelectronic Properties of Phenanthroline‐Based Thermally Activated Delayed Fluorescence Emitters through Isomer Engineering

“…[6,7,14,20,24] Although promising results have been achieved on TADF emitters with the state-of-art external quantum efficiencies (η ext s) close to those of phosphorescent OLEDs, the further improvement in the device efficiency and stability is still in demand, and the insight into the relationship between the TADF molecular structures and properties is to be deepened. [10,[24][25][26][27][28] Phenanthroline derivatives have been widely used as efficient electron-transporting materials, [29,30] good host materials, [31,32] and ligand of phosphorescent emitters [33][34][35][36][37][38] in OLEDs, in virtue of their efficient electron transporting properties, good thermal stability, rigid planar structure, and easy structure modification. In this article, we designed and synthesized three isomeric phenanthroline derivatives (as shown in Scheme 1, collectively named x-PXZP, x = o, m, p), i.e., 2,9-di(10H-phenoxazin-10-yl)-1,10-phenanthroline (o-PXZP), 3,8-di(10H-phenoxazin-10-yl)-1,10-phenanthroline (m-PXZP), and 4,7-di(10H-phenoxazin-10-yl)-1,10-phenanthroline (p-PXZP), with phenoxazine (PXZ) unit linked to the ortho-, meta-and para-position of nitrogen atoms in highly rigid phenanthroline core, in which PXZ unit is widely used electron donor in TADF emitters for its strong electron-donating ability and suitable steric hindrance.…”