Control of magnetoconductance through modifying the amount of dissociated excited states in tris-(8-hydroxyquinoline) aluminum-based organic light-emitting diodes

Chen, P.; Lei, Yanlian; Song, Qunliang; Zhang, Q. M.; Zhang, Y.; Liu, R.; Xiong, Zuhong

doi:10.1063/1.3430044

Cited by 8 publications

(7 citation statements)

References 16 publications

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“…The ultrathin layer has no effect on I – V characteristics, which is clearly shown in Figure a. Because the singlet excitons formed on Alq 3 could efficiently transfer to C545T by Förster energy transfer and the excitons formed on Alq 3 and C545T have different dissociation rates due to their different binding energy, − it is expected that the MC of the device with ultrathin layer is different from that of device without ultrathin layer. Figure b shows the MC of the two devices measured at the same voltage.…”

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confidence: 98%

Electron–Hole Pair Model in Bulk-Limited Organic Light-Emitting Diodes

2014

J. Phys. Chem. C

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By using an Al quenching layer to control the exciton concentration, we obtained the direct evidence of electron−hole pair model in organic light-emitting diodes. The use of ultrathin sensing layer further illustrated that magnetoconductance is from dissociation of singlet excitons We used the space-charge-limited conductance (SCLC) transport model to theoretically study the line shape of magnetoconductance and found that in addition to hyperfine field the electron/hole mobility and space charge effect could also change the line shape of magnetoconductance. M agnetic field effects (MFEs) in organic light-emitting diodes (OLEDs) have been observed in 2003, 1 since then, substantial advances have recently been made. In OLEDs, both electroluminescence and conductance have been shown to be depended on the applied magnetic field. 2−9 This interesting effects caused extensive experimental and theoretical research. Various possible mechanisms for magnetoconductance (MC) and magnetic electroluminescence (MEL) have emerged from these studies, such as electron−hole pair model, 10−12 bipolaron model, 7,13−16 and spin dependence of triplet−triplet annihilation (TTA). 17−19 Recent studies suggest that the hyperfine interaction is responsible for the MC and MEL 11,12 In this paper, we studied the MC and MEL behaviors of ITO/N,N′-bis(lnaphthyl)-N,N′-diphenyl-1,1′-biphentl-4,4′-diamine (NPB)/tri-(8-hydroxyquinoline)aluminum (Alq 3 )/LiF/Al by introducing a thin metal quenching layer and a dye sensing layer at the proper position in NPB/Alq 3 layers. By comparison of the MFEs in different devices, it is considered the electron− hole pair model is suitable for our Alq 3 emitting devices. We further used the SCLC transport model to theoretically study the line shape of MC and found that electron−hole mobility and space charge effect could change the line shape of MC.The studied devices here were fabricated by vacuum thermal evaporation on clean indium tin oxide (ITO) patterned glass substrates. 50 nm NPB and 50 nm Alq 3 were chosen as the hole transporting layer and the electron transporting/light emitting layer, respectively. Aluminum (Al) was chosen as the cathode, and 1 nm LiF near the Al cathode was used as buffer layer to increase electron injection. 3 nm Al and 0.2 nm 2,3,6,7-t e t r a h y d r o -1 , 1 , 7 , 7 -t e t r a me t h y l -1 H , 5 H , 1 1 H -1 0 -( 2 -benzothiazolyl)quinolizino[9,9a,1gh]coumarin (C545T) were used as the quenching layer and the sensing layer, respectively.All measurements were performed at room temperature under ambient condition.In order to reveal the role of excitons in MC and MEL in device ITO/NPB/Alq 3 /LiF/Al, we first inserted a 3 nm Al at the interface between NPB and Alq 3 as exciton quenching layer, which should be a more intuitive way for comparison. Figure 1a shows the schematic of device ITO/NPB/Al/Alq 3 /LiF/Al. Figure 1b shows the current−luminance−voltage (C-L-V) properties of our device. There is no observable electroluminescence at low applied voltages, and a faint electroluminescenc...

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confidence: 98%

Electron–Hole Pair Model in Bulk-Limited Organic Light-Emitting Diodes

2014

J. Phys. Chem. C

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“…e) 中可以看出, 室温下 (T = 300 K) 两种器件呈现出类似的线型, 即: 当 |B| < 25 mT 时, MEL 值均随着磁场的增加而小幅减小; 当 25 mT < |B| < 300 mT 时, MEL 值随着磁场的增加而逐渐增加, 直到 B 增加到 300 mT 时的 MEL 值也未达到饱和, 这种变化趋势与文献报道的 STT 过程决定的指纹式响应曲线一致 [12] . ISC 过程决定的 MEL 指纹式曲线一致 [13] ; 而在高场效应的变化中, MEL 曲线随磁场逐渐增加的趋势则是由 STT 过程决定的, 反之, 逐渐减小的趋势则是由 TTA 过程决定的 [19] . 由于两器件对应 MEL 曲线的高场变化更为明显, 因此本文主要研究高场, 而对低场不做过多讨论.…”

Section: 注入电流和工作温度对器件 Mel 曲线的影响unclassified

Study of the microscopic mechanism of Ir(ppy)$_{3}$ regulating exciton splitting and luminescence process in Rubrene

Tang

Zhu

et al. 2020

Sci. Sin.-Inf.

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Ir(ppy) 3 的单、三重态激子能级和发射谱以及 Rubrene 吸收谱的分析可知, 器件中除了 Rubrene 分子间距会影响 STT 过程的强弱外, 还包括由 Ir(ppy) 3 强的 SOC 导致的激子间的系间穿越 (intersystem crossing, ISC) 和 Ir(ppy) 3 的 T 1 激子与 Rubrene 的 S 1 激子间的能量传递 (energy transfer, ET) 过程, 这 3 种微观机制的共同作用导致了器件 MEL 和发光的复杂变化, 且电流密度的大小和器件工作温度的高低对它们还有较好的调控作用. 显然, 本研究有助于深入理解基于红荧烯光电器件的微观过程及其演化机制.

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“…陷于CBP能级之中, 产生能级陷阱. 因此, CBP中的激发态可通过能级陷阱捕获和Fӧrster能量转移两种方式 [17,18] , 将能量传递给DCM形成客体分子的激发别是主要由系间窜越((inter-system crossing, ISC)和 TQI中散射过程所引起 [15,16,18,19] . 其中ISC过程比TQI 16,19] .…”

Section: 近10年来许多研究组在不同的有机半导体材unclassified