Trap state-assisted electron injection in blue quantum dot light-emitting diode

We report trap state-assisted electron injection in a blue quantum dot light-emitting diode (QLED) in this work. By replacing an electron transport layer and a quantum dot emission layer, we identify trap states are indeed on blue quantum dots. We also analyze the equivalent circuit model and the density of trap state distribution by impedance spectroscopy. Furthermore, the trap states induce charge transfer in the blue QLED and lower the device efficiency, suggesting the competition between electron injection and trapping in a working device. Our work shows a distinct electron injection mechanism in blue QLEDs that has not been shown in red and green QLEDs.