Positive temperature dependence of the electroluminescent performance in a colloidal quantum dot light-emitting diode

Abstract

In this study, the temperature dependence of the dynamic behavior in colloidal quantum dot light-emitting diodes (QLEDs) in a wide temperature range (120 K–300 K) is investigated. The results demonstrate that the electroluminescent performance of the device is enhanced as the temperature rises. Particularly, the device current efficiency is improved and the turn-on voltage is lowered. In addition, the decline in temperature results in a blue-shift of the electroluminescence spectrum. Consequently, the charge injection barrier is studied using thermionic emission model and impedance spectroscopy, and the results show that this injection barrier increases when the temperature is elevated, leading to more difficult charge injection. Meanwhile, the charge transport study proves that the average charge lifetime in the device is prolonged at higher temperature, which is beneficial for the transport of charges. Furthermore, the analyses of the trap states and their distribution reveal that more trap states exist at low temperature, causing performance degradation in the device. The analysis and discussion in this work provide fundamental insights into the working mechanism of QLEDs and can be used to predict device performance under extreme operating conditions.