Highly Efficient Blue Light Emitting Cd-free Colloidal Quantum-Well and its Application to the Electroluminescent Devices
Journal
CHEM MATER
Date
2020.06.23
Abstract
To obtain highly efficient, stable, and environmentally friendly blue light emitting materials for display applications, we prepared specially tailored Cd-free, colloidal quantum well (CQW) structure of ZnS/ZnTeSe/ZnS. We optimized the synthetic methods to make very uniform ZnS core having a diameter of ~2.9 nm within 10 ％ of the size distribution. And, it was found that the ZnS QD structures were either a cube with (100) surface facets or a tetrahedron with (111) facets. As the ZnTeSe mid-shell grew on the ZnS core surface, the CQW maintained initial facet and shape of the core. The photoluminescence of the CQW could be tuned from 375 nm to 458 nm by controlling the thickness of the ZnTeSe mid-shell. And, 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 high quantum yield (QY) up to 85％ and the narrow spectrum width of 23 nm at 446 nm. Moreover, we fabricated a light-emitting diodes (LED) device with the CQW, and it showed the external quantum efficiency of 5.2 ％ at 5000 cd/m2 with the brightness of 6210 cd/m2 at 6.4V.