量子点
光电子学
发光二极管
二极管
激子
电子
材料科学
电容
介电谱
物理
电极
凝聚态物理
电化学
量子力学
作者
Xiangwei Qu,Guohong Xiang,Jingrui Ma,Pai Liu,Aung Ko Ko Kyaw,Kai Wang,Xiao Wei Sun
摘要
Unlike red and green quantum dot light-emitting diodes (QLEDs), it is not clear whether a blue QLED is an electron-dominated device. In this work, we identify that electron is over-injected in blue QLEDs by impedance spectroscopy. By analyzing the capacitance–voltage characteristics of the single-carrier devices, we find that the built-in voltage of the electron-only device is smaller than that of the hole-only device. Therefore, electron injection is more efficient than hole injection in blue QLEDs. To support our arguments, we employ a red QD as a fluorescent sensor to spatially investigate the exciton recombination zone of a blue QLED. Consequently, we observe that the exciton recombination zone of the blue QLED is close to the hole transport layer, and it shifts toward an electron transport layer with the increase in the applied bias. Our work provides a practical method for identifying the excess carrier in blue QLEDs, and it could be applied to other types of QLEDs.
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