According to a study published in Light Science & Applications, an effective interlayer sensitization strategy for blue MR-TADF emitters has been developed by a group of scientists led by Professor Zujin Zhao from South China University of Technology in Guangzhou, China. The strategy involves separating the TADF sensitizer and the MR-TADF emitter into two adjacent emitting layers (EMLs) with different hosts. TADF sensitizers can sensitize MR-TADF emitters through long-range Förster energy transfer (FET).
a, Schematic illustrations of interlayer-sensitizing system for blue MR-TADF emitters. b, Molecular structures of MR-TADF emitters and TADF sensitizers employed in the interlayer-sensitizing configuration. c, Device configuration of interlayer-sensitized hyperfluorescence devices. Image Credit: Jianghui Wang, Peng Zou, Letian Chen, Zhentao Bai, Hao Liu, Wen-Cheng Chen, Yanping Huo, Ben Zhong Tang and Zujin Zhao
Materials with thermally activated delayed fluorescence (MR-TADF) and multi-resonances show promise as narrow electroluminescence (EL) spectra for organic light-emitting diodes (OLEDs).
Chinese scientists have successfully realized blue hyperfluorescence OLEDs with excellent color quality and exceptional EL efficiencies simultaneously by using an interlayer sensitization approach to enhance the EL efficiencies of blue MR-TADF emitters with blue MR-TADF sensitizers.
The results show that the interlayer sensitization technique is a potential approach for creating high-performance blue hyperfluorescence OLEDs.
MR-TADF emitters are potential options for OLEDs with narrow EL spectra. However, many MR-TADF emitters suffer from severe triplet-involved quenching processes, which reduce EL efficiencies and produce fast efficiency roll-offs. Many recent studies aim to overcome this issue by synthesizing hyperfluorescence OLEDs.
However, for optimizing blue MR-TADF emitters, the current sensitization strategy of co-doping MR-TADF emitters with TADF sensitizers in the same wide-energy-gap host layer might not be the best option as the polarity of a single host might be incompatible with both blue TADF sensitizer and blue MR-TADF emitter.
Based on this interlayer sensitization strategy, high-performance hyperfluorescence OLEDs are prepared using various blue MR-TADF emitters and TADF sensitizers. These produce strong blue light with narrow EL spectra and outstanding external quantum efficiencies (EQEs) of up to 38.8%, which appear to be superior to those of unsensitized devices.
These findings show that this interlayer sensitization technique could create blue hyperfluorescence OLEDs with high EL efficiency and color purity.
Journal Reference:
Wang, J., et. al. (2024) Promising interlayer sensitization strategy for the construction of high-performance blue hyperfluorescence OLEDs. Light Science & Applications. doi:10.1038/s41377-024-01490-6