A seed-mediated and double shell strategy to realize large-size ZnSe/ZnS/ZnS quantum dots for high color purity blue light-emitting diodes.

Environment-friendly high color purity blue zinc selenide (ZnSe) quantum dot-based light-emitting diodes (QLEDs) are promising candidates in next-generation display applications. However, due to the large bandgap of ZnSe (2.7 eV), the reported electroluminescence (EL) wavelengths of ZnSe QLEDs are mainly located within the range from purple to violet blue, and preparing blue emitting (>445 nm) ZnSe QLEDs remains challenging. Herein, we report a seed-mediated and double shell strategy to synthesize large-sized blue ZnSe/ZnS/ZnS core/shell/shell quantum dots (QDs). The as-prepared QDs possess excellent features including narrow full widths at half-maximum (11-19 nm), tunable emission wavelengths (410-451 nm), and high photoluminescence quantum yields (≥50%). Using ZnSe/ZnS/ZnS QDs as emitters in an inverted device, a color saturated blue QLED with an EL wavelength of 446 nm, a maximum luminance of 106 cd m, a current efficiency of 0.94 cd A, and an EQE of 2.62% is successfully fabricated. These results indicate that blue ZnSe QLEDs have great potential for future display technologies.