利用红荧烯激子能量共振分析三重态激子-电荷作用的磁电导机制

发布时间：2018-10-20 14:04

【摘要】：为了研究三重态激子与电荷作用(triplet-charge interaction,TCI)产生磁电导(magneto-conductance,MC)的原因,分别用Al,Li F/Al和Ca等不同功函数的金属作为阴极制作了一系列红荧烯(rubrene)型有机发光器件.在室温下Al电极器件中出现了随磁场增加单调下降的负MC.器件的电流-电压特征曲线表明,Al电极器件中空穴为多余载流子,电子注入困难易形成陷阱电荷.利用rubrene中单重态激子(singlet,S)和三重态激子(triplet,T)的能量共振改变S激子裂变(STT)和T激子聚变(TTA)来调控T激子的比率,并通过更换阴极来改变电子注入势垒高度从而调控电荷(charge,C)的浓度,最终实现对TCI的调控.调控结果表明,Al电极器件中负的MC不应该是T激子与多余空穴通过解离或者散射通道的TCI引起的,而是T与陷阱中的束缚电子通过TCI的去陷阱(T+C_t→S_0+C)通道淬灭导致的.另外,载流子注入较为平衡的Li F/Al和Ca电极器件的MC比Al电极器件的小1个量级,且随磁场的增加先减小后增大,这并非是因为平衡注入器件内的TCI弱,而是由于器件内rubrene功能层中的陷阱容易被电子占满,TCI去陷阱淬灭通道和陷阱捕获淬灭通道对电流的影响变低.因此,载流子陷阱在TCI的磁效应中具有重要地位,使有机功能层中的陷阱尽量多且不易被载流子占满是利用TCI磁效应的重要方向.
[Abstract]:In order to study the reason why triplet excitons interact with charge (triplet-charge interaction,TCI) to produce magnetic conductance (magneto-conductance,MC), a series of red fluorene (rubrene) type organic luminescent devices were fabricated by using different work function metals such as Al,Li F/Al and Ca as cathodes. At room temperature, negative MC. decreases monotonously with the increase of magnetic field in Al electrode devices. The current-voltage characteristic curves show that the holes in the Al electrode device are superfluous carriers and the trap charge is easily formed when the electron injection is difficult. Using the energy resonance of single state exciton (singlet,S) and triplet exciton (triplet,T) in rubrene, the ratio of S exciton fission (STT) and T exciton fusion (TTA) is changed to regulate the ratio of T exciton, and the concentration of charge (charge,C) is regulated by changing the electron injection barrier height by changing the cathode. Finally, the control of TCI is realized. The results show that the negative MC in Al electrode devices should not be caused by T excitons and redundant holes by dissociating or scattering channel TCI, but by the quenching of T and trapped electrons through TCI channels. In addition, the MC of the more balanced Li F/Al and Ca electrode devices with carrier injection is one order of magnitude smaller than that of the Al electrode devices, and decreases first and then increases with the increase of magnetic field, which is not due to the weak TCI in the balanced injection devices. However, because the traps in the rubrene functional layer are easily occupied by electrons, the effect of TCI detrap quenching channel and trap quenching channel on the current is reduced. Therefore, carrier traps play an important role in the magnetic effect of TCI. Making the traps in organic functional layers as much as possible and not easily occupied by carriers is an important direction to utilize the magnetic effect of TCI.
【作者单位】：西南大学物理科学与技术学院;
【基金】：国家自然科学基金(11374242) 中央高校基本业务费专项(XDJK2015C149)资助
【分类号】：TN303

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