Fraunhofer ENAS has been working for many years on the fabrication of light emitting diodes based on semiconductor nanocrystals, so-called quantum dots (QDs), for special applications.
Due to their excellent properties, such as narrow band emission (high color purity), high chemical stability and spectral tunability of the emission with the particle size, QDs are very well suited as emitters and nanoprobes for sensor applications. A prominent application of QD nanoprobes is the detection of heavy metals such as lead or cadmium in aqueous environments, as pursued in a current project at Fraunhofer ENAS. In addition, QD-LEDs are optimized for various applications, including spectral sensing (ENAS patents US 10217890 B2, DE 102014221525 B4), distance detection or fabrication on special substrates.
Typically, QD-LED preparation is done by combining both solvent and gas-phase based deposition methods under an inert gas atmosphere, which allows coating of rigid substrates such as glass, flexible substrates such as film, or even planarized textiles. Using the micro-imprint process, the segmented deposition of multiple LEDs with different emission wavelengths on a common substrate is also easily possible.