Chinese scholars have made progress in the field of narrowband OLED research

Figure Molecular structure of narrow-band luminescent materials and their OLED device properties

With the support of the National Natural Science Foundation of China (grant numbers: 52130308, 91433201, 91833304, 51125013), Professor Yang Chuluo's team at Shenzhen University has made progress in the field of narrowband OLED research, and the relevant results are "Efficient selenium-integrated TADF OLEDs with.
" Reduced roll-off" published online in Nature Photonics on October 14, 2022
.
Links to papers: https://doi.
org/10.
1038/s41566-022-01083-y
.

In recent years, multiple resonance thermally activated delayed fluorescence (MR-TADF) materials have great application potential
in high-definition display due to their narrow-band emission characteristics.
However, the reverse intersystem transition rate (kRISC) of multiple resonance TADF materials is generally slow, resulting in a sharp attenuation of the efficiency of light-emitting devices at high brightness, which makes it difficult for the corresponding OLED devices to combine the advantages
of high efficiency, high color purity and low roll-off.

In order to solve the key problem of efficiency roll-off, Professor Yang Chuluo's team of Shenzhen University synthesized BNSeSe by embedding non-metallic heavy atom selenium in a multi-resonance framework, and used the heavy atom effect to enhance the coupling between the mono- and trilinear (S1 and T1) orbitals of the material, so as to achieve extremely high kRISC (2.
0?).
× 10^{6 s-1}) and photoluminescence quantum efficiency (100%)
.
The external quantum efficiency of the evaporated OLED device prepared by BNSeSe as the guest material of the light-emitting layer is as high as 36.
8%, and its efficiency roll-off is effectively suppressed, and the external quantum efficiency is 34% at 1000 cd ^m-2 brightness, and the external quantum efficiency is still as high as 21.
9% even at 10000 cd ^m-2 brightness, which is comparable to iridium, platinum and other phosphorescent material devices
。 Further, they prepared a superfluorescent OLED device for the first time using a multiplex-resonant TADF material as a sensitizer, the maximum external quantum efficiency of the device is 40.
5%, the external quantum efficiency is 32.
4% at 1000 cd m-2 brightness, even at 10000 cd m-2 brightness, the external quantum efficiency is still as high as 23.
3%, and the maximum power efficiency exceeds 200 lm ^W-1.
The maximum brightness is close to 200000 cd ^m-2
.
This work provides a new idea and effective way to solve the efficiency roll-off problem of MR-TADF electroluminescent devices, and has a good application prospect in high-definition display (figure).