Increasing energy barrier between quantum dots for enhancing non-carrier-injection electroluminescence

Quantum dot (QD) light-emitting devices operating in non-carrier-injection electroluminescence (NCI-QDEL) mode have attracted attention due to their extremely simple structure and excellent stability. However, the working mechanisms of the QD-based NCI-QDEL still require further improvement, especially regarding the transfer process of charges between QDs. Noting that there are plenty of salt compounds and organic ligands between QDs during the solution synthesis, which must have an influence on the device performance by impacting the charge transfer process. Thus, it is necessary to reveal effect of the QD surrounding states on the NCI-QDEL performance. In this work, effect of the purification process on the surrounding states of QDs is investigated, and the charge transfer process is elucidated according to the NCI-QDEL performance. It is found that a moderate energy barrier between QDs is helpful to improve NCI-QDEL. We propose a working mode of the QD-based NCI-QDEL, in which the salt compounds and organic ligands between QDs are equivalent to QD-QD energy barriers that can adjust the charge transfer process and increase the electron-hole overlap probability. We believe that this work can provide guidance for the design and fabrication of QDs suitable for NCI devices. •Effect of the QD surrounding states on the NCI-QDEL performance is investigated.•Effect of the purification process on the surrounding states of QDs is investigated.•A moderate energy barrier between QDs is helpful to improve NCI-QDEL.•A modified working mode of the QD-based NCI-QDEL is proposed.