An external quantum efficiency of >20% from solution-processed poly(dendrimer) organic light-emitting diodes

Abstract

Controlling the orientation of the emissive dipole has led to a renaissance of organic light-emitting diode (OLED) research, with external quantum efficiencies (EQEs) of >30% being reported for phosphorescent emitters. These highly efficient OLEDs are generally manufactured using evaporative methods and are comprised of small-molecule heteroleptic phosphorescent iridium(III) complexes blended with a host and additional layers to balance charge injection and transport. Large area OLEDs for lighting and display applications would benefit from low-cost solution processing, provided that high EQEs could be achieved. Here, we show that poly(dendrimer)s consisting of a non-conjugated polymer backbone with iridium(III) complexes forming the cores of firstgeneration dendrimer side chains can be co-deposited with a host by solution processing to give highly efficient devices. Simple bilayer devices comprising the emissive layer and an electron transport layer gave an EQE of >20% at luminances of up to ≈300 cd/ m 2 , showing that polymer engineering can enable alignment of the emissive dipole of solution-processed phosphorescent materials.

Synthesis, Characterization, and Physical Properties of Pyrene‐Naphthalimide Derivatives as Emissive Materials for Electroluminescent Devices

“…The EL spectra coincided well with the PL profiles of the EML in a thin film, indicating that emission originates from the same chromophore and suggestive that there were no strong optical cavity effects. The absence of the emission peaks at lower wavelengths due to the CBP host molecule at 385 nm [42] and TmPyPB layer at 396 nm [38] denotes a sole emitter emission. Besides, for each device, the EL spectra's shape and maximum wavelength remained unchanged under different applied voltages.…”

Carbon Dots: An Insight into Their Application in Heavy Metal Sensing

“…The investigation of novel CDs with different passivation agents has improved their photophysical properties while maintaining their low toxicity. For example, the application of CDs in light-emitting diode (LED) technology is an area of increasing interest due to its efficiency in energy consumption [37][38][39]. The most important component of LED devices is a sandwich-type structure known as the emitting layer, which is made of different organic and organic-inorganic materials with extraordinary emission properties, high photostability, and optimal external quantum efficiency (EQE) [3,40].…”

High-Efficiency Diphenylpyrimidine Derivatives Blue Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes

“…The reason that the efficiency of the device is approximately four times different is due to three reasons as follows: First, the improved device efficiencies in 2,6-PhPMAF doped device is caused by fast upconverted triplet excitons to the singlet state with relatively smaller E ST of 0.17 eV compared to 0.27 eV in 4,6-PhPMAF dopant. Second is that it is believed to be due to improved internal quantum efficiency by the relatively higher PLQY value of the 2,6-PhPMAF (29.5%) emitter than 4,6-PhPMAF (16.9%) because the device efficiency is depends on the solid-state PLQY of the emitter, as discussed in literatures (de Sá Pereira et al, 2017;Maasoumi et al, 2018). As mentioned in the azimuthal intensity distributions, finally, it can be explained because the relatively narrow FWHM of DPEPO:2,6-PhPMAF film compared with the DPEPO:4,6-PhPMAF film has relatively horizontal plane-on orientation to the substrate, resulting in improved outcoupling efficiency in the emitting layer.…”