High‐Efficiency Single Emissive Layer White Organic Light‐Emitting Diodes Based on Solution‐Processed Dendritic Host and New Orange‐Emitting Iridium Complex

Abstract

An extremely high-efficiency solution-processed white organic light-emitting diode (WOLED) is successfully developed by simultaneously using an ideal dendritic host material and a novel efficient orange phosphorescent iridium complex. The optimized device exhibits forward-viewing efficiencies of 70.6 cd A(-1) , 26.0%, and 47.6 lm W(-1) at a luminance of 100 cd m(-2) , respectively, promising the low-cost solution-processed WOLEDs a bright future as the next generation of illumination sources.

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

“…However, their thin-film assemblies, most of which are amorphous in nature, are easily broken up, even by the orthogonal solvents, because small molecules typically attach to each other only by weak intermolecular forces such as van der Waals, H-bonding and p-p stacking interactions. Consequently, the highest reported efficiency of solution-processed smallmolecule OLEDs still relies on a vacuum-evaporated electrontransporting layer (ETL), which is not practical for low-cost mass production of scalable devices 26 .…”

P‐159: Triplet Exciton Confinement in White Phosphorescent Organic Light‐Emitting Diodes with Multi‐Doped Single Emissive Layer

“…The ITO glass was cleaned in an ultrasonic bath by the regular cleaning sequences: in deionized water, isopropyl alcohol, acetone, deionize water, isopropyl alcohol, thereafter, the pre-cleaned ITO glass was treated with O 2 plasma under vacuum conditions of 5.0 × 10 -2 Torr, of 50W for 2 minutes and then MoO 3 as HIL was deposited by thermal evaporation. All organic materials were deposited by thermal evaporation technique under a pressure of (Firpic), Tris(2-phenylpyridine)iridium(III) (Ir(ppy) 3 ), and Tris(1-phenylisoquinoline)iridium(III) (Ir(piq) 3 ) as primary color blue, green and red doped into mCP, respectively and 2',2',2''-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) as electron transfer layer and 8-Hydroxyquinolinolato-lithium (Liq) as electron injection layer, respectively. Then aluminum cathode electrode was deposited by thermal evaporation with evaporation rate of 5.0Å/s.…”

“…5 depicts EL spectra of the device A, B and C at 6V, 8V and 10V each. Blue and green emissions at 470nm and 500nm were increased as driving voltage increased, which means triplet energy transferred from FIrpic and Ir(ppy) 3 to Ir(piq) 3 . Then triplet excitons were emitted by Ir(piq) 3 at 590nm but remained excitons after emission can be transferred back to FIrpic and Ir(ppy) 3 generating additional emission at 470nm and 500 nm [6].…”

“…As saturated with intensity of EL peak at 590nm, EL intensity of device A, B and C show that energy transfer process happened from saturated molecules to non-saturated molecules. As saturated Ir(piq) 3 , Ir(ppy) 3 and FIrpic in EML of device C in regular sequence, firstly, Triplet excitons of Ir(piq) 3 diffused to TAPC, Ir(ppy) 3 , FIrpic and mCP. Then secondly triplet excitons of Ir(ppy) 3 diffused to TAPC, FIrpic and mCP, and finally triplet excitons of FIrpic diffused to TAPC and mCP examining EL peak intensity of the devices A, B and C depicted in Fig.…”

“…This is achieved by harvesting both singlet and triplet excitons that are four times more than fluorescent organic light-emitting diodes (FLOLEDs). However, white PHOLEDs are needed to be optimized for high performance in commercial applications [1][2][3]. Confining triplet excitons in white PHOLEDs have been studied to achieve higher efficiency.…”