Highly efficient organic light-emitting diodes and light-emitting electrochemical cells employing multiresonant thermally activated delayed fluorescent emitters with bulky donor or acceptor peripheral groups  

作　　者：Jingxiang Wang Hassan Hafeez Shi Tang Tomas Matulaitis Ludvig Edman Ifor D.W.Samuel Eli Zysman-Colman 

机构地区：[1]Organic Semiconductor Centre,EaStCHEM School of Chemistry,University of St Andrews,St Andrews,Fife,UK [2]Organic Semiconductor Centre,SUPA School of Physics and Astronomy,University of St Andrews,St Andrews,UK [3]The Organic Photonics and Electronics Group,Department of Physics,UmeåUniversity,Umeå,Sweden

出　　处：《Aggregate》2024年第5期233-244,共12页聚集体（英文）

基　　金：Engineering and Physical Sciences Research Council,Grant/Award Numbers:EP/R035164/1,EP/W007517/1,EP/W015137/1;China Scholarship Council,Grant/Award Number:202006250026;Swedish Energy Agency,Grant/Award Numbers:50779-1,P2021-00032;Swedish Research Council,Grant/Award Numbers:2019-02345,2021-04778;European Research Council,Grant/Award Number:101096650;Knut och Alice Wallenbergs Stiftelse,Grant/Award Number:WISE-AP01-D02。

摘　　要：Multiresonant thermally activated delayedfluorescence(MR-TADF)emitters have been the focus of extensive design efforts as they are recognized to show bright,narrowband emission,which makes them very appealing for display applications.However,the planar geometry and relatively large singlet–triplet energy gap lead to,respectively,severe aggregation-caused quenching(ACQ)and slow reverse intersys-tem crossing(RISC).Here,a design strategy is proposed to address both issues.Two MR-TADF emitters triphenylphosphine oxide(TPPO)-tBu-DiKTa and tripheny-lamine(TPA)-tBu-DiKTa have been synthesized.Twisted ortho-substituted groups help increase the intermolecular distance and largely suppress the ACQ.In addition,the contributions from intermolecular charge transfer states in the case of TPA-tBu-DiKTa help to accelerate RISC.The organic light-emitting diodes(OLEDs)with TPPO-tBu-DiKTa and TPA-tBu-DiKTa exhibit high maximum external quan-tum efficiencies(EQEmax)of 24.4%and 31.0%,respectively.Notably,the device with 25 wt%TPA-tBu-DiKTa showed both high EQEmax of 28.0%and reduced efficiency roll-off(19.9%EQE at 1000 cd m^(-2))compared to the device with 5 wt%emitter(31.0%EQEmax and 11.0%EQE at 1000 cd m^(-2)).The new emitters were also introduced into single-layer light-emitting electrochemical cells(LECs),equipped with air-stable electrodes.The LEC containing TPA-tBu-DiKTa dispersed at 0.5 wt%in a matrix comprising a mobility-balanced blend-host and an ionic liq-uid electrolyte delivered blue luminance with an EQEmax of 2.6%at 425 cd m^(-2).The high efficiencies of the OLEDs and LECs with TPA-tBu-DiKTa illustrate the potential for improving device performance when the DiKTa core is decorated with twisted bulky donors.

关 键 词：aggregation-caused quenching electroluminescence long-range charge transfer OLED organic semi-conductor short-range charge transfer TADF 

分 类 号：TN312.8[电子电信—物理电子学]