Zuhong Xiong

Although high‐efficiency blue fluorescent TBPe‐based organic light‐emitting diodes (OLEDs) are reported, the microscopic mechanisms of excited states in TBPe emitters remain vague. Here, using fingerprint magneto‐electroluminescence probing tools, hot excitons and their high‐level reverse inter‐system crossing (HL‐RISC, S ₁ ←T ₂ ) and triplet fusion (T ₂ F, T ₂ +T ₂ →S _n →S ₁ ) in TBPe are discovered for the first time, which is also consistently demonstrated by their transient‐electroluminescence. Interestingly, all their rich microscopic physical behaviors can be reasonably explained within the framework of excited state dynamics involved in these TBPe‐based OLEDs. The carrier mobility, polarity, and triplet energy of host materials can significantly affect the number of generated T _2,TBPe hot‐excitons and thus the probabilities of HL‐RISC and T ₂ F channels, which are further modulated by exothermic low‐level Dexter energy transfer (DET) or endothermic high‐level DET channels of cold or hot excitons. Moreover, utilizing the HL‐RISC channel of hot excitons in TBPe dopants with the conventional low‐level RISC channel of an exciplex co‐host, a relatively high external quantum efficiency of 7.09% is achieved from blue fluorescent TBPe‐doped OLEDs. Thus, this work renews the physical understanding of the microscopic evolution channels of excited states in TBPe emitters and lays a solid foundation for further designing high‐efficiency blue fluorescent OLEDs.

Although both organic and perovskite light‐emitting diodes (OLEDs and PeLEDs) are rapidly developed, OLEDs are more stable and PeLEDs possess larger carrier mobility compared with each other. Naturally, combining their respective advantages is crucial for the device photoelectric performances. Here, an intriguing electroplex system comprising an organic donor and a 0D perovskite (0D‐Cs ₄ PbBr ₆ ) acceptor is demonstrated by probing fingerprint magnetic field effects and transient/steady electroluminescence spectroscopies of control devices and Cs‐Pb‐Br films. Such a clear role division in this newly‐found electroplex system makes it possible to integrate their own advantageous properties into a single optoelectronic device (organic‐perovskite light‐emitting diodes, O‐Pe‐LEDs). Interestingly, the 0D‐Cs ₄ PbBr ₆ acceptor is transformed from the typical 3D CsPbBr ₃ (3D‐CsPbBr ₃ ) by annealing treatment and can revert to 3D‐CsPbBr ₃ under atmospheric exposure. This reversible phase transition leads to abundant optical, electrical, and magnetic behaviors of O‐Pe‐LEDs. More importantly, these O‐Pe‐LEDs are fabricated by an all‐thermal evaporation deposition technique, which is demonstrated as the most feasible route for simultaneously achieving high‐resolution pixels and large‐scale production. Therefore, this innovation of organic‐perovskite electroplexes opens an unprecedented research direction for developing high‐performance commercial LEDs for lighting and flat‐panel displays.

为探究多种激发态共存体系中空穴传输层(hole-transporting layer, HTL)对热激子通道的影响, 本文选用具有热激子特性的红荧烯材料为发射体, 不同三重态能量的材料作为HTL, 制备了一系列激基复合物和激子态共存的红荧烯掺杂发光器件. 同时, 还制备了常规激子型红荧烯掺杂器件作为对比. 通过测量不同温度和电流下电致发光的特征磁场效应(magneto-electroluminescence, MEL)曲线发现, 当发光层主体三重态能量高而HTL三重态能量[E(T1,HTL)]低时, 激子型器件的低场(|B|<9 mT) MEL曲线仅表现为系间窜越过程(intersystem crossing, ISC)决定的线型, 而多种激发态共存器件的MEL低场主要由ISC决定, 但其超低场(|B|<3 mT)还存在较弱的高能态反向系间窜越过程(high-level reverse intersystem crossing, hRISC, 即高能三重态激子T2到最低单重态激子的热激子通道, T2→S1); 当激基复合物主体三重态能量[E(EX3,host)]和E(T1,HTL)都较高时, 多种激发态共存器件的MEL低场只由hRISC决定; 相反, MEL低场只由ISC过程决定. 分析各功能层间的激发态能量转移与损失机制可知: 多种激发态共存器件中激子复合区与HTL相距较远, 导致E(T1,HTL)很难直接影响红荧烯热激子T2态的数量, 但其与E(EX3,host)间的能量转移通道不可忽略. 也就是, 当E(T1,HTL)较低时, 激基复合物主体到HTL的能量损失通道[E(EX3,host)→E(T1,HTL)]将抑制主客体间的Dexter能量转移过程, 不利于T2态的形成, 最终减弱甚至完全抑制热激子的hRISC过程. 本研究将加深对多种激发态共存体系中热激子演化物理行为的理解, 并为高性能红荧烯黄光器件(一种重要的照明光源)的结构设计提供新思路.

In this paper, we propose a scheme based on the spin Hall effect of light (SHEL) for characterizing aligned polymers. Poly (3-hexylthiophene) (P3HT) films were prepared via the solution shear coating method. The experimental results obtained by using SHEL indicated that the alignment of polymer chains could be enhanced by UV irradiation and was positively correlated with the irradiation time, which was consistent with the measurements of the UV–Vis spectrometer and the polarizing optical microscope (POM). Compared with other optical methods, such as POM that characterizes aligned samples using light intensity, the amplified shift in SHEL can significantly reduce technical noise and exhibit high sensitivity. Even for the weak alignment film, this method can still recognize its alignment and achieve a signal-to-noise ratio (SNR) of 30 dB. This renders SHEL a highly precise technique for studying aligned polymers, which is valuable for the development of organic electronics.