ZnS Nanocrystal‐Mediated Spacing and Band Engineering for Efficient and Stable Blue ZnSeTe QLEDs

ZnSeTe quantum dot light‐emitting diodes (QLEDs) are promising candidates for environmentally friendly display applications. However, their electroluminescence performance and practical implementation are still hindered by nonradiative recombination originating from exciton trapping at defect states among quantum dots (QDs) in the emissive layer (EML). Herein, wide‐bandgap ZnS nanocrystals are incorporated into the ZnSeTe EML to suppress nonradiative recombination and modulate carrier transport, thereby improving the performance of blue ZnSeTe QLEDs. The results reveal that the introduction of ZnS nanocrystals effectively suppresses Förster resonance energy transfer among QDs within the EML, leading to an extension of the exciton lifetime in the film from 9.2 to 12.7 ns. Meanwhile, the built‐in electric field established at the interface between ZnS nanocrystals and ZnSeTe QDs induces upward band bending in the EML, which lowers the hole injection barrier and facilitates more balanced carrier transport. As a result, the resulting blue QLEDs deliver a luminance of 10229.4 cd m −2 at 6 V, a maximum external quantum efficiency of 21.2% at 2317.4 cd m −2 , and a T 50 lifetime of 220.2 h at an100.0 cd m −2 , compared with 49.9 h for the control device. This work offers an effective strategy for developing high‐performance blue environmentally friendly QLEDs.