Fully solution-processed red tandem quantum dot light-emitting diodes with an EQE exceeding 35%

Abstract

Compared to conventional quantum dot light-emitting diodes (QLEDs), tandem QLEDs (TQLEDs) have the advantages of long lifetime, high brightness and high efficiency, thereby making them potential candidates for display and lighting applications. In this work, ZnMgO/PEDOT:PSS was employed as the interconnecting layer (ICL) to fabricate TQLEDs, achieving brightness doubling at the equivalent current. Further, the devices exhibited a maximum external quantum efficiency (EQE) of 35.51%, which is currently the largest EQE reported for the full-solution process of manufacturing red TQLEDs. The improvement in TQLED efficiency can be attributed to the optimization of the electronic transport layer (ETL), which is achieved by adjusting the Mg doping level in ZnO. This process facilitated a balanced electron and hole injection and limited the photoluminescence (PL) quenching of QDs by ZnO. Furthermore, it can also be attributed to the effective charge generation capacity of ZnMgO/PEDOT:PSS along with the resistance of ZnMgO to acids.