摘要
把三重态激子(T1)与单重态激子(S1)能量接近的典型热辅助延迟荧光材料4CzTPN-Ph作为掺杂客体,以具有不同T1能量的材料分别作为掺杂主体、空穴传输层和电子传输层,制备了一系列基于4CzTPN-Ph掺杂的有机发光二极管,并测量了这些器件在室温下的磁电致发光效应(Magneto-Electroluminescence, MEL)和磁电导效应(Magneto-Conductance, MC),以及器件随温度变化的MEL和MC.实验发现:室温下,当空穴传输层、电子传输层和掺杂主体分别选用T1能量高低不同的材料时,各器件的MEL和MC在低磁场范围(|B|<20 mT)分别呈现出不同变化规律的线型,具体表现为当器件各功能层同时都选用较高T1能量的材料时,器件MEL的幅度在低磁场范围内表现出随注入电流的减小而变小的反常行为,并出现了由正到负的转变, MC曲线则表现出符号为负且其幅度随磁场的增加而变大的RISC属性;而当器件的空穴传输层、电子传输层或掺杂主体材料的三重态能量较低时, MEL和MC表现出减弱的RISC过程;并且,当电子传输层或掺杂主体选用三重态能量与4CzTPN-Ph接近的Alq3时, MEL和MC直接表现出类似未掺杂的Alq3荧光器件的线型.分析器件的能量传输过程可知, T1能量高低不同的空穴传输层、电子传输层或掺杂主体材料对4CzTPN-Ph三重态能量的束缚能力不同,造成各器件中T1激子不同的传输通道和能量损失,从而使各器件在低磁场范围出现了不同的MEL和MC线型.本研究不仅丰富了能量传输对4CzTPN-Ph发光器件内部机制的认识,同时也对TADF器件中三重态激子的可控应用提供了一定的理论参考.
4CzTPN-Ph is a kind of typical thermally activated delayed fluorescence (TADF) material with a small energy gap between its singlet and triplet levels of the charge-transfer states (CTs). In this paper, we used 4CzTPN-Ph as dopant and materials with different triplet exciton (T1) energy as host, hole-transporting layer (HTL) or electron-transporting layer (ETL) to fabricate a series of 4CzTPN-Ph-doped organic light-emitting diodes (OLEDs). The magneto-electroluminescence (MEL) and magneto-conductance (MC) from these devices were measured with different bias currents at room temperature, and with various temperatures at a fixed injection current. The experimental results demonstrated that when the materials with different T1 energy are selected as the HTL, ETL and doping host, the MEL and MC of these devices exhibited various line-shapes with different variation tendency within low magnetic fields (|B|<20 mT), respectively.When each functional layer of the OLEDs with high「energy, the amplitude of MEL curves showed abnormal behavior that reduced with decreasing injection currents at low magnetic field, and could convert from positive to negative. At the same time, the MC traces showed typical RISC process where the MC value was negative and rapidly enhanced with increasing magnetic field. However, when the HTL, ETL or host were selected with low T1 energy materials, the MEL and MC of devices showed weakened RISC process. Especially, when Alq3, whose T1 energy is close to that of 4CzTPNPh, was used as the ETL or host, the MEL and MC traces of devices directly presented the line-shape that was similar to that of pure Alq3-based fluorescent devices. By analyzing the energy transfer process of spin-pair states in these studied OLEDs,we found that the HTL, ETL and host materials with different T1 energy could limit the T1 energy of 4CzTPNPh with different intensity, causing different energy transfer channel and energy loss of T1 in devices. Consequently, MEL and MC of these devices were diverse from each other in low
作者
邓金秋
汤仙童
许静
潘睿亨
胡叶倩
熊祖洪
DENG JinQiu;TANG XianTong;XU Jing;PAN RuiHeng;HU YeQian;XIONG ZuHong(School of Physical Science and Technology,Southwest University,Chongqing 400715,China)
出处
《中国科学：物理学、力学、天文学》
CSCD
北大核心
2019年第6期67-79,共13页
Scientia Sinica Physica,Mechanica & Astronomica
基金
国家自然科学基金(编号:11874305,11374242)资助项目
关键词
热活化延迟荧光
磁电致发光效应
磁电导效应
反向系间窜越
三重态激子
能量传输
thermally activated delayed fluorescence
magneto-electroluminescence effects
magneto-conductance effects
reverse intersystem crossing
triplet exciton
energy transfer
