High efficiency and low roll-off green OLEDs with simple structure by utilizing thermally activated delayed fluorescence material as the universal host

Abstract

Abstract:We achieved high-efficiency and low-roll-off green fluorescent and phosphorescent organic lightemitting diodes (OLEDs) simultaneously by adopting the thermally activated delayed fluorescence material of bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone as the universal host. At a luminance of 1000 cd/m 2 , fluorescent OLEDs based on C545T get a current efficiency, power efficiency, and external quantum efficiency (EQE) of 31.8 cd/A, 25.0 lm/W, and 9.26%, respectively. This is almost the highest efficiency based on C545T at the luminance of 1000 cd/m 2 to date. On the other hand, phosphorescent OLEDs with Ir(ppy) 3 as the emitter realize a maximum current efficiency, power efficiency, and EQE of 64.3 cd/A, 62.4 lm/W, and 18.5%, respectively. More important, the EQE remains 17.8% at the representative luminance of 1000 cd/m 2 and the roll-off ratio is just 3.78%. The transient photoluminescence decay measurement demonstrates that the up-conversion of host triplet excitons plays a key role in the high efficiency and low roll-off. More detailed discussions are also given.

Quinolinylmethanone-Based Thermally Activated Delayed Fluorescence Emitters and the Application in OLEDs: Effect of Intramolecular H-Bonding

“…One the frequently observed issues is the severe efficiency roll-off at a practical brightness level, the other is the poor color purity . Although many TADF devices show high efficiency at low brightness (1 cd/m 2 ), the efficiency drops very rapidly at practical brightness level (100 cd/m 2 ). , In addition, most TADF molecules show broad emission spectrum with a full width at half-maximum (fwhm) of nearly 100 nm . A molecule can harvest both singlet (S 1 ) and triplet (T 1 ) excitons for light emitting, if the triplet can undergo fast reverse intersystem crossing (RISC) to the singlet via thermal activation. , The molecule with this property is called a TADF emitter.…”

High-efficiency all-fluorescent white organic light-emitting diode based on TADF material as a sensitizer

“…16,17 Recently, the rapid development of TADF materials provided a promising route to improve the efficiency of conventional uorescent-based OLEDs by adopting TADF materials as sensitizers, which promotes the application of all-uorescent WOLEDs in at panel display and lighting products. [18][19][20][21][22][23] In TADF-sensitized uorescent OLEDs, TADF materials with twisted electron donor-acceptor (D-A) structures possess ambipolar carrier transport ability, which benets the improvement of the carrier balance. On the other hand, TADF as a sensitizer can help to separate the RISC of TADF material and light-emitting of uorescent materials, and the efficient Förster energy transfer (FRET) from TADF sensitizer to uorescent guest benets to achieve excellent device performance.…”

Use of Hybrid PEDOT:PSS/Metal Sulfide Quantum Dots for a Hole Injection Layer in Highly Efficient Green Phosphorescent Organic Light-Emitting Diodes

“…To date, many research groups have used the solution processed hole injection layer (HIL) to improve the device performance and to decrease the fabrication costs ( Li et al, 2018 ; Hu et al, 2020 ; Wang et al, 2020 ). To obtain the highly efficient OLEDs, the overall requirements on solution processed HIL should possess excellent optical and electrical characteristics such as high transparency and conductivity, as well as the low surface roughness ( Zhao et al, 2016 ; McEwan et al, 2018 ; Feng et al, 2020 ). Therefore, the synthesis and development of solution processed hole injection materials are very important to achieve high-performance devices.…”