Highly ordered inkjet-printed quantum-dot thin films enable efficient and stable QLEDs with EQE exceeding 23%

Abstract

Inkjet-printed quantum dot light-emitting diodes (QLEDs) are emerging as a promising technology for next-generation displays. However, the progress in fabricating QLEDs using inkjet printing technique has been slower compared to spin-coated devices, particularly in terms of efficiency and stability. The key to achieving high performance QLEDs lies in creating a highly ordered and uniform inkjet-printed quantum dot (QD) thin film. In this study, we present a highly effective strategy to significantly improve the quality of inkjet-printed CdZnSe/CdZnS/ZnS QD thin films through a pressure-assisted thermal annealing (PTA) approach. Benefiting from this PTA process, a high quality QD thin film with ordered packing, low surface roughness, high photoluminescence and excellent electrical property is obtained. The mechanism behind the PTA process and its profound impact on device performance have been thoroughly investigated and understood. Consequently, a record high external quantum efficiency (EQE) of 23.08% with an impressive operational lifetime (T₅₀) of up to 343,342 ​h@100 ​cd ​m⁻², and a record EQE of 22.43% with T₅₀ exceeding to 1,500,463 ​h@100 ​cd ​m⁻² are achieved in inkjet-printed red and green CdZnSe-based QLEDs, respectively. This work highlights the PTA process as an important approach to realize highly efficient and stable inkjet-printed QLEDs, thus advancing QLED technology to practical applications.