Multi-dimensional quantum materials: From Dots to Rods, Sheets and Giant Shell Particles

S. Krohn, H. Schlicke, T. Jochum, J. Niehaus
Fraunhofer CAN,
Germany

Keywords: quantum material, quantum dot, QD, quantum rod, quantum sheet, QLED, polarized emission, display

Summary:

Since 2013 zero-dimensional, spherical quantum dots (QDs) are used by the display industry for high-end devices with improved color gamut compared to non-QD LED TVs. In contrast, the next generation of optoelectronic devices will most likely be based on quantum materials with superior core/shell structures like “Dot-in-GiantShell” (GS-QD), “Dot-in-Rod” (DR) or “Dot-in-Sheet” (DS) nanoheterostructures. These particles offer unique optical properties like narrow band widths, high stability, increased brightness, huge absorption coefficient in the blue, polarized emission and on/off switchability in an electric field. For producing these next generation particles Fraunhofer CAN has established a platform technology based on continuous flow to allow automating of the synthesis. This ensures the reproducibility and throughput needed to investigate their use in new optoelectronic applications. We will present how this technique is set-up and explain how the different geometries of the above mentioned particles are achieved. In case of the Giant Shell particles we will show results for particles with diameters between 10 and 20 nm including TEM analysis, especially the influence of the diameter on quantum yield and absorption characteristics. In case of the elongated Quantum Rods we will show results for green and red emitting particles with different aspect ratios including TEM analysis and quantum yields. We will also show measurements proving the degree of polarization (DOP) on a single particle level and the DOP results for aligned QR film on 1 cm2 electrodes. In case of the Quantum Sheets we will present TEM and quantum yield measurements and compare their properties to the 0D and 1D particles mentioned above. To underline their different behaviors in applications, we will also show results for electroluminescent qLED devices manufactured with these 0D, 1D and 2D particles and compare them to each other.