Elongated quantum rods: polarized emission for novel display applications

J. Niehaus, T. Jochum, H. Weller
CAN GmbH,
Germany

Keywords: QD, rod, LED, display, quantum

Summary:

For producing these elongated nanostructures, we have developed a reliable synthesis route based on continuous flow technology. This synthesis technique offers several advantages over traditional batch synthesis like satisfying industrial demand regarding quality, quantity and reproducibility. For advanced materials like CdSe/CdS nanoheterostructures little synthetic variations results in big structural differences and poor material performance. Therefore we want to highlight the synthetic approach of the continuous flow reactor as universal tool for up-scaling DRs fabrication. The huge elongated CdS shell acts as a photon antenna for wavelengths < 450nm leading to the enormous absorption in that area. The huge extinction coefficient of the DRs at 450 nm is a further outstanding feature for liquid crystal display (LCD) applications. Quantum yield values up to 96 % and FWHM values smaller than 35 nm can be reached by measuring the DRs in solution. As a unique feature of these nanorods the emission is polarized due to the elongated surrounding shell and the negligible band offset between CdSe core and CdS shell material. At room temperature our synthesized DRs offer a polarization degree between 80 – 90°. Working with single particle spectroscopy allows on the one hand in-depth insights into the fluorescence properties of DRs and on the other hand a quality seal for our continuous flow synthesis.Single CdSe/CdS nanorods were detected by confocal microscopy measuring the fluorescence intensity at different angles of the polarizer. Here we present the synthesis for CdSe/CdS rods with emission wavelengths of 530 nm, 560 nm, 590 nm and 620 nm and the variation of the aspect ratio. We will show the correlation of QY to emission color and aspect ratio. We will also show how the aspect ratio influences the degree of polarization of the emitted light. The specific data show the potential of the DRs as next promising tool for optoelectronic devices.