摘要
采用不同浓度的热活化延迟荧光(thermally activated delayed fluorescence,TADF)材料2,3,5,6-四(3,6-二苯基-9-咔唑基)-对苯二腈(2,3,5,6-tetrakis(3,6-diphenylcarbazol-9-yl)-1,4-dicyanobenzene,4CzTPN-Ph)为掺杂剂,三(8-羟基喹啉)铝(tris-8-hydroxyquinoline aluminum,Alq3)为主体材料制备了发光层为Alq3:x%4CzTPN-Ph的有机发光二极管器件,并测量了室温下不同注入电流和不同掺杂浓度,以及固定某一电流和掺杂浓度在不同温度下器件的磁电致发光(magneto-electroluminescence,MEL)效应和磁电导(magneto-conductance,MC)效应.实验发现,在主客体掺杂类型器件中,与普通掺杂器件减小的磁效应相比,这种器件具有明显的反常磁效应——即表现出增强的MEL和MC幅值.以室温下注入电流为150μA的实验为例,发光层为Alq3:5%4CzTPN-Ph器件的MEL幅值在磁场为300m T处达到了10%左右,大约是参考器件(发光层为CBP:5%4CzTPN-Ph)的MEL幅值(~0.75%)的13倍,且该器件对应的MC幅值在磁场为300 m T处达到了6%左右,大约是此参考器件MC幅值(~0.12%)的50倍.此外,这种掺杂器件的MEL和MC明显受到掺杂浓度的调控,当掺杂浓度达15%左右时,MEL和MC幅值可达到最大值.在不同温度下,这种掺杂器件的MEL和MC值均随着温度的降低而减小.通过分析器件的能级结构和光谱可知,Alq3:4CzTPN-Ph器件具有主客体分子间特殊的能级排布,造成客体分子的能级陷阱较弱,外加磁场抑制三重态激子对电荷的散射作用(TQA)就可产生显著的MEL和MC幅值,从而得到不同于普通掺杂器件的反常磁效应.此外,由于TQA过程受三重态激子浓度与载流子浓度的影响,掺杂浓度和实验温度也能通过影响三重态激子浓度和载流子浓度来对TQA反应强弱进行调控,从而有效地调控这种反常磁效应.本研究工作有助于深入理解基于4CzTPN-Ph发光器件微观机制的演化过程,并将促进有机发光二极管在磁学器件方面的应用.
Organic magnetic field effects （OMFEs）, which primarily to-conductance （MC）, is a non-contact, non-destructive and includes magneto-electroluminescence （MEL） and magnesensitive tool for probing the mechanisms that occur within in organic light-emitting diodes （OLEDs）. Not only OMFEs can be used to detect charge transport, exciton evolution and luminescence mechanisms in OLEDs, and can also be used in magnetic devices, including magnetic switches, magnetic storage and magnetic sensors, etc. Stable magnetic devices are usually required for practical applications. There is a wealth of research that shows that doped devices exhibit improved stability when compared with non-doped devices, however, they always show weaker OMFEs responses. Therefore, it is important to achieve strong OMFEs responses from stable, doped devices. In this work, we have fabricated OLEDs using the thermally activated delayed fluorescence （TADF） material 2,3,5,6-tetrakis（3,6-diphenyl-carbazol-9-yl）-1,4-dicyanobenzene （4CzTPN-Ph） of different doping concentration as the dopant, and either tris-8-hydroxyquinoline aluminum （Alq3） and 4,4＇-N,N＇-dicarbazole-biphenyl （CBP） as the host materials. The light-emitting layer in these OLEDs was Alq3 ：x% 4CzTPN-Ph （studied devices） or CBP： 5% 4CzTPN-Ph （reference device）. The MEL and MC curves from these devices were measured with different injection currents and doping concentrations at room temperature, and with varying temperatures at a constant injection current and doping concentration. Compared with the reduced OMFEs observed from the reference device, the studied devices exhibited increased amplitudes in their MEL and MC responses. For example, at an injection current of 150 μA at room temperature, the amplitude of the MEL from the studied device reached -10% when exposed to a magnetic field of 300 mT, which was approximately 13 times larger than that observed from the reference device （-0.75%）. The corre- sponding amplitude from the MC from t
作者
邓金秋
汤仙童
潘睿亨
胡叶倩
朱洪强
熊祖洪
陈晓莉
Jinqiu Deng;Xiantong Tang;Ruiheng Pan;Yeqian Hu;Hongqiang Zhu;Zuhong Xiong;Xiaoli Chen(School of Physical Science and Technology,Southwest University,Chongqing 400715,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2018年第28期2974-2984,共11页
Chinese Science Bulletin
基金
国家自然科学基金(11374242)
中央高校基本科研业务费专项(XDJK2017D141)资助
关键词
热活化延迟荧光材料
磁电致发光效应
磁电导效应
散射过程
能级陷阱
thermally activated delayed fluorescence materials
magneto-electroluminescence effects
magneto-conductance effects
scattering process
energy level trap
