A Thermally Activated Delayed Fluorescence Green OLED with 4500 h Lifetime and 20% External Quantum Efficiency by Optimizing the Emission Zone using a Single‐Emission Spectrum Technique

Abstract

are thought to limit the performance of phosphorescent OLEDs and TADF OLEDs. [10,11] During OLED operation, the triplet-polaron interaction causes undesirable efficiency roll-off (i.e., increased quenching of excited states at higher current densities) and degradation (e.g., increasing the number of molecules with some of their intramolecular bonds irreversibly dissociated), resulting in less emitted light. Understanding and managing exciton dynamics is therefore of great significance in the design of modern TADF OLEDs. [12,13] These internal nanoscale processes are often difficult to observe, so there is

Highly efficient and stable green fluorescent OLEDs with high color purity using a BODIPY derivative

“…In this context, through sophisticated device engineering, a representative green TADF emitter, 4CzIPN , exhibited high stability with an LT 50 of over 10 000 h at a high brightness of 1000 cd m −2 . 8,9 Therefore, a 4CzIPN -based hyperfluorescence system is one of the most promising devices for realizing stable and high-efficiency OLEDs with high color purity. Duan et al developed a 4CzIPN -based hyperfluorescence system using tPhBODIPY with an EQE of 19% and narrow FWHM of 32 nm; however, its stability was limited to 3000 h at 1000 cd m −2 .…”

“…Meanwhile, in order to realize the long-term stability, higher concentration of 4CzIPN ( ca. 20 wt%) is generally needed, 8,9 and higher concentration causes lower PLQY and EQE due to the concentration quenching. In our case, the PLQY value was recorded to be 79% in the 0.5 wt% tPhBODIPY / 4CzIPN / mCBP film (Table S1†).…”

“…6 They used high color purity green emitter tPhBODIPY , with an FWHM of 28 nm, combined with TADF sensitizer 4CzIPN , and they realized an EQE max /LT 50 @1000 cd m −2 of 19%/2947 h. Additionally, the same group developed a pure green OLED using MR-TADF emitter AZA-BN combined with Ir(ppy) 3 as a sensitizer, 7 realizing an FWHM of 30 nm and EQE max /LT 90 @1000 cd m −2 of 28%/156 h, which is almost similar to the lifetime of tPhBODIPY -based devices. However, compared with corresponding conventional TADF OLEDs with an EQE of over 20% and LT 50 @1000 cd m −2 of over 30 000 hours, 8,9 the stability of high-efficiency and high-color-purity OLEDs remains a challenging task.…”

Extremely-low-voltage, high-efficiency and stability-enhanced inverted bottom OLEDs enabled via a p-type/ultra-thin metal/n-doped electron injection layer

“…When Al, Ag and MoO 3 are inserted between F 4 -TCNQ and BPhen:Li, the barriers decrease to 0.12 eV, 0.42 eV and 0.48 eV, respectively. Therefore, electrons can easily arrive at the EML due to the low energy barrier of F 4 -TCNQ/Al/BPhen:Li EIL, 39 resulting in low voltages in Device C.…”

Simple excited-state modification toward a deep-blue hybridized local and charge-transfer (HLCT) fluorophore and non-doped organic light-emitting diodes

“…Great efforts have been made by both academia and industry; the third-generation high-efficiency and low-cost pure organic fluorescent materials including thermally activated delayed fluorescence (TADF), [6][7][8][9][10][11] triplet-triplet annihilation (TTA), [12][13][14][15] hybridized local and charge-transfer (HLCT), [16][17][18][19][20][21][22][23] and organic radical-based emitters 24,25 have been rapidly developed. However, the new synthesis methods and categories of stable luminescent radicals are very limited, and their emission wavelengths are confined to the red and near-infrared regions.…”