基于Diels-Alder反应的可交联空穴传输材料的合成及其在聚合物发光二极管中的应用

设计合成了一种侧链含呋喃的可交联共轭聚合物空穴传输材料聚{2,7-9,9-二(6-(2-呋喃甲氧基)己基)芴]-共-4,4′-(4″-丁基)三苯胺}(P1)和侧链含马来酰亚胺的共轭小分子交联剂N,N′-二4-(6-马来酰亚氨基己基)苯基]-N,N′-二苯基联苯二胺(M1).基于呋喃和马来酰亚胺间Diels-Alder反应,P1和M1共混膜可在150°C下热处理快速交联形成具有优异抗溶剂性的薄膜,同时薄膜的光电性能可以通过控制P1和M1的共混比例进行有效调节.器件研究结果表明,基于P1+M1交联的薄膜表现出了优异的空穴传输、电子阻挡性质,应用于聚合物发光二极管时可有效避免由传统空穴传输材料聚3,4-亚乙二氧基噻吩/聚苯乙烯磺酸(PEDOT:PSS)作为单一界面层引起的发光淬灭现象,使相应器件性能得到大幅提升.当M1添加量为10%时,相关器件表现出了最佳的器件性能,器件的最大电流效率为9.0 cd A~(-1),最大亮度为35681 cd m~(-2),启亮电压为3.2 V.

Synthesis of Cross-linkable Hole-transporting Materials Based on Diels-Alder Reaction and Their Application in Polymer Light-emitting Diodes

One of the most challenging tasks in the fabrication of multilayer polymer light-emitting diodes (PLEDs) by solution process is to avoid the interfacial mixing between different layers.To overcome this challenge,extensive efforts have been made in developing crosslinkable materials for PLEDs.However,considering the unfavorable effects of their harsh crosslinking conditions on device performance,it is still desirable to design crosslinkable materials with moderate cured condition to satisfy the requirements of printing device in large scale in the future.Herein,a crosslinkable conjugated polymer with hole-transporting property,poly9,9-bis(6-furfuryloxyhexyl)-9H-fluorene-co-4,4'-(4"-butyltriphenylamine)] (P1) with furan pendant side chains,and a small molecule crosslinker,N,N'-bis4-(6-maleimidohexyl)phenyl]-N'-di-phenylbenzidine (M1) with maleimide functional group,were developed.Due to the fast Diels-Alder reaction between the maleimide in M1 and the furan group in P1,the blend films of P1 and M1 can be quickly crosslinked in extremely short time,resulting in robust hole transporting layer (HTL) films with good solvent resistance,which can overcome the interface mixing problem in solution processed multilayer PLEDs.Such a moderate cured condition (heated at 150 ℃ for ～ 1 min) can decrease negative effects and the optoelectronic property of the resulting HTL film can be tuned also by changing the ratio of the small molecular crosslinker (5％-100％;maleimide/furan).The PLEDs,with the structure of ITO/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/P1 + M 1/emmisive layer/Ba/A1,were fabricated to investigate the effects of the crosslinker ratio on device performance.The device study results indicated that the HTLs based on P1 + M1 exhibited excellent hole-transporting/electron blocking properties and can prevent emission quenching caused by PEDOT:PSS in the traditional PEDOT:PSS based PLEDs.When M1 content is below 10％,the device displayed lower Von,higher Bmax and LEmax,and the device with HTL based on P1 + 10％ M1 exhibited the best performance with LEmax of 9.0 cd A-1,Bmax of 35681 cd m-2 and Von of 3.2 V,with a higher brightness of 5000 cd Tm-2.Our results indicated that the Diels-Alder reaction between the maleimide and the furan groups can be used to prepare optoelectronic materials for solution processed multilayer engineering ofoptoelectronic devices,such as PLEDs,polymer solar cells etc..