Rational molecular design of efficient yellow-red dendrimer TADF for solution-processed OLEDs: a combined effect of substitution position and strength of the donors  

作　　者：Changfeng Si Dianming Sun Tomas Matulaitis David B.Cordes Alexandra M.Z.Slawin Eli Zysman-Colman 

机构地区：[1]Organic Semiconductor Centre,EaStCHEM School of Chemistry,University of St Andrews,St Andrews,KY169ST,UK

出　　处：《Science China Chemistry》2024年第5期1613-1623,共11页中国科学（化学英文版）

基　　金：the China Scholarship Council(201806890001);support from the Royal Academy of Engineering Enterprise Fellowship (EF2122-13106);EPSRC (EP/W015137/1, EP/W524505/1) for financial support。

摘　　要：The development of high-performance solution-processed red organic light-emitting diodes(OLEDs) remains a challenge,particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized four novel orange-red thermally activated delayed fluorescence(TADF) dendrimers that are solution-processable: 2GCz BP, 2DPACz BP, 2FBP2GCz and 2FBP2DPACz. We systematically investigated the effect of substitution position and strength of donors on the optoelectronic properties. The reverse intersystem crossing rate constant(kRISC) of the emitters having donors substituted at positions 11and 12 of the dibenzo[a,c]phenazine(BP) is more than 10-times faster than that of compounds substituted having donors substituted at positions 3 and 6. Compound 2DPACz BP, containing stronger donors than 2GCz BP, exhibits a red-shifted emission and smaller singlet-triplet energy splitting, ΔE_(ST), of 0.01 e V. The solution-processed OLED with 10 wt% 2DPACz BP doped in m CP emitted at 640 nm and showed a maximum external quantum efficiency(EQE_(max)) of 7.8%, which was effectively maintained out to a luminance of 1,000 cd m-2. Such a device's performance at relevant display luminance is among the highest for solution-processed red TADF OLEDs. The efficiency of the devices was improved significantly by using 4Cz IPN as an assistant dopant in a hyperfluorescence(HF) configuration, where the 2DPACz BP HF device shows an EQEmaxof 20.0% at λEL of 605 nm and remains high at 11.8% at a luminance of 1,000 cd m-2, which makes this device one of the highest efficiency orange-to-red HF SP-OLEDs to date.

关 键 词：thermally activated delayed fluorescence solution-processing red OLEDs dibenzo[a c]phenazine DENDRIMERS 

分 类 号：TN383.1[电子电信—物理电子学] TQ317[化学工程—高聚物工业]