Effective exciplex system with high emission efficiency via intramolecular hydrogen bonding for efficient solution processable OLEDs  

基于分子内氢键的高发光效率的激基复合物体系实现高效率溶液加工型有机电致发光二极管

作　　者：Xiaoyi Lai Junqing Wang Xiaolong Liu Lei Hua Bin Li Weiguo Zhu Jun Yeob Lee Yafei Wang 赖晓翼;王俊清;刘小龙;华磊;李斌;朱卫国;Jun Yeob Lee;王亚飞(School of Materials Science&Engineering,Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering,Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications,Changzhou University,Changzhou 213164,China;School of Chemical Engineering,Sungkyunkwan University,Suwon,Gyeonggi,16419,Republic of Korea;SKKU Institute of Energy Science and Technology,Sungkyunkwan University,Suwon,Gyeonggi,16419,Republic of Korea)

机构地区：[1]School of Materials Science&Engineering,Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering,Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications,Changzhou University,Changzhou 213164,China [2]School of Chemical Engineering,Sungkyunkwan University,Suwon,Gyeonggi,16419,Republic of Korea [3]SKKU Institute of Energy Science and Technology,Sungkyunkwan University,Suwon,Gyeonggi,16419,Republic of Korea

出　　处：《Science China Materials》2024年第11期3543-3552,共10页中国科学（材料科学）（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(22371020 and 52073035);the Special Program for Foreign Talents in Changzhou City(CQ20224052)。

摘　　要：Exciplex system is a charming candidate for thermally activated delayed fluorescence(TADF)due to its intrinsic small energy difference between the lowest singlet state and triplet excited state(ΔEST).However,high emission efficiency and fast radiative decay rate are still a formidable task for the exciplex emission.Herein two novel tri(triazolo)triazine-based TADF emitters,named TTT-HPh-Ac and TTTMePh-Ac,are synthesized and characterized.Using such TADF emitters as the donor molecule and(1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-dial)tris(diphenylphosphine oxide)(PO-T2T)as the acceptor molecule,the exciplex system of TTT-HPh-Ac:PO-T2T and TTT-MePh-Ac:PO-T2T are prepared,which show a tinyΔEST of 40±20 meV and fast reverse intersystem crossing rate.As a result,very high emission efficiency(97%)and a small non-radiative decay rate are detected for the exciplex TADF system.The solution processable organic light-emitting diode using the exciplex system as the emitter achieves a maximum external quantum efficiency(EQE_(max))of 17.0%.When using the exciplex as the host matrix,the TTT-MePh-Ac:PO-T2T based solution processable device shows a better performance with an EQE_(max)of 20%with a very small efficiency roll-off of 6%at 1000 cd m^(−2).This work proves that the molecule with both intramolecular hydrogen bonding and proper twisted molecular geometry in exciplex is more favorable to enhance its emission efficiency and suppress the non-radiative transition,which provides a new way to develop efficient and stable exciplex emitters.激基复合物体系因其具有较小的单/三线态能隙差(ΔE_(ST))而成为热活化延迟荧光(TADF)材料的研究重点.然而,获得高发光效率和高辐射跃迁速率仍是激基复合物体系的难点.为了改善上述存在问题,本文设计合成了两种基于三(三唑)并三嗪单元的TADF材料TTT-HPh-Ac和TTT-MePh-Ac;并以这两种TADF材料为给体分子,以PO-T2T为受体分子,制备了两类激基复合物体系TTT-HPh-Ac:PO-T2T和TTTMePh-Ac:PO-T2T.该材料体系具有极小的ΔE_(ST)值,快速的系统间反向交叉速率和非常高的发光效率(97%).以这类激基复合物为发光材料,其溶液加工型有机发光二极管获得了17.0%的最大外量子效率(EQE_(max));以激基复合物作为主体材料时,基于TTT-MePh-AcPO-T2T的溶液加工器件呈现出更好的性能,其EQE_(max)为20%,且在1000 cd m^(-2)时的效率滚降非常小,仅为6%.本研究证明了同时具有分子内氢键和扭曲分子几何结构的分子更有利于提高激基复合物的发光效率,这为开发高效稳定的激基复合物体系提供了新的途径.

关 键 词：exciplex system thermally activated delayed fluorescence tris(triazolo)triazine intramolecular hydrogen bonding solution-processable OLED 

分 类 号：TN383.1[电子电信—物理电子学] TB34[一般工业技术—材料科学与工程]