Study on stability of wurtzite CdZnS/ZnS quantum rod and enhancing stability

Abstract

Blue emitting CdZnS/ZnS quantum rod has 450nm of emission wavelength, narrow FWHM(~30nm). And it has unique properties compared to quantum dots. Emission of quantum rod can be modulated by using external electric field. And it has better energy efficiency than quantum dot because of large stokes shift. In this regard quantum rod also can be used to various light emitting application. But there are some critical problems for CdZnS quantum rod. As its aspect ratio is increasing, Its PL Quantum yield is decreasing. And its stability is low-ering as increasing aspect ratio. For applying to device, enhancing PL QY stability is very important. To enhance stability of CdZnS/ZnS quantum rod, we investigated proper shell precursors for ZnS shell growth. Finally, we choose two-step shell growth method and proper precursor for ZnS shell. For better optical properties, we synthe-sized inner ZnS shell by using Zinc sulfate heptahydrate. For outer shell growth, we changed Zinc precursor and S precursor to enhance stability of ZnS shell. Using Zinc nitrate hexahydrate and TOP-S, we can grow ZnS shell more. Stability after two-step growth was increased much longer than one-step ZnS shell growth. In addition to increasing stability(5 times than before), its PL intensity also increased(over 40%). This result is expected to form uniform ZnS shell entirely on CdZnS surface after two-step growth.