Identifying the dominant carrier of CdSe-based blue quantum dot light-emitting diode

Unlike red and green quantum dot light-emitting diodes (QLEDs), it is not clear whether a blue QLED an electron-dominated device. In this work, we identify that electron over-injected in QLEDs by impedance spectroscopy. By analyzing the capacitance–voltage characteristics of single-carrier devices, find built-in voltage electron-only device smaller than hole-only Therefore, injection more efficient hole QLEDs. To support our arguments, employ QD as fluorescent sensor to spatially investigate exciton recombination zone QLED. Consequently, observe close transport layer, shifts toward layer with increase applied bias. Our work provides practical method for identifying excess carrier QLEDs, could be other types