Small and sensitive: multiple protection strategies for light emitting quantum dots

Onderzoeksgroepen: Lumilab en CoCoon

Promotoren: Prof. Philippe Smet en Prof. Christophe Detavernier

Begeleiding: Robin Petit

Inlichtingen: tel. 09/264.43.42 of contacteer rechtstreeks een betrokken persoon (de contactgegevens opvragen door op de naam te klikken)

 

Quantum dots (QD) or semiconductor nanocrystals are steadily taking over the lighting industry. Due to their many advantageous properties over other current technologies, they are quickly becoming potential candidates for applications such as Luminescent Solar Concentrators (LSC), lasers and light-emitting diodes (LED). It is envisioned their importance will only continue to grow.

Despite their promising opto-electronic properties, QD are highly sensitive to their immediate environment. Possible unwanted reactions can lead to a decrease in the QD optical performance over time and efforts to make the QD more stable are deemed necessary. Their use in applications often requires the QD to be embedded in a host matrix (polymer thin film). Furthermore, to shield the QD from their surroundings (oxygen and water diffusion) an inorganic barrier is grown. One of the most promising techniques used for this is atomic layer deposition (ALD). In this way, the QD luminescent properties are safeguarded, ensuring a long device lifetime.

A further advancement is the use of a multilayer barrier. Here the barrier consists of alternating organic and inorganic layers, preventing crack propagation throughout the structure while increasing the path length for diffusion. Within this Master Thesis this type of barrier is developed and investigated.

Small and sensitive: multiple protection strategies

Initially, the deposition of both the organic and inorganic (single) layers is performed and the resulting thin films are characterized. The most suitable polymers will be selected and cast into thin films using spin coating, while ALD will be used to grow the inorganic layers (Al2O3, TiO2, ZnO). The successful incorporation of the QD into the polymer thin film strongly depends on the polymer backbone and the QD surface chemistry and will be evaluated. The QD are provided through a partnership with the Department of Chemistry (WE06) (no QD synthesis is required during this Master Thesis). Different techniques are applicable for the structural, morphological or otherwise optical characterization of the thin films: fourier transform infrared spectroscopy, ellipsometry, UV-Vis spectroscopy, X-ray reflectivity, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and many more. Careful data-analysis will be key in obtaining the most information out of these complementary techniques.

Eventually the transition to a multilayer barrier is made. You will propose and realize specific compositions depending on the desired properties of the resulting stack. A comparison of the barrier performance between a single barrier and the multilayer barrier is envisioned based on degradation studies of the QD optical performance. Depending on the properties of the organic and inorganic layers and the number of QD-polymer layers different devices can be developed and investigated.

Opmerkingen:

  • Dit thesisonderwerp kan ook opgenomen worden in het kader van de Educatieve Master Fysica en Sterrenkunde.
  • Aan dit onderwerp is geen mobiliteitsaspect verbonden. Er kan met de promotoren wel overlegd worden over gerelateerde stage-activiteiten en/of vakken aan andere universiteiten.