Efficient Blue-Light-Emitting Cd-Free Colloidal Quantum Well and Its Application in Electroluminescent Devices

To obtain highly efficient, stable, and environmentally friendly blue-light-emitting materials for display applications, we prepared a specially tailored Cd-free, colloidal quantum-well (CQW) structure of ZnS/ZnTeSe/ZnS. We optimized the synthetic methods to construct a very uniform ZnS core having a diameter of similar to 2.9 nm within 10% of the size distribution. In addition, it was found that the ZnS QD structures were either a cube with the (100) surface facets or a tetrahedron with the (111) facets. As the ZnTeSe mid-shell grew on the ZnS core surface, the CQW maintained the initial facet and shape of the core. The photoluminescence of the CQW could be tuned from 375 to 458 nm by controlling the thickness of the ZnTeSe mid-shell. Furthermore, the spectral width changed depending on the Te composition in the ZnTeSe. After the final ZnS shell passivation, the optimized blue-light-emitting CQW showed a high quantum yield (QY) of up to 85% and a narrow spectrum width of 23 nm at 446 nm. Moreover, we fabricated light-emitting diodes (LEDs) with the CQW and demonstrated an external quantum efficiency of 6.8% at 3.6 V with a maximum brightness of 14 146 cd/m(2) at 8 V.