Colloidal quantum dots (QDs) are semiconductor nanoparticles with quantum confined properties. Due to the interesting opto-electronic properties of these QDs, they are applied in both light emitting devices (displays, lasers) as well as in light absorbing applications (solar cells, photodetectors). The material can be stabilized in a solution by capping the QDs with a ligand. As a result, low temperature solution processing on any surface becomes possible. Our research targets solution-processed thin-films QD photodetectors, sensitive to infrared light, processed directly on optimized silicon read-out circuitry. In such a structure, the QD photodetector absorbs IR photons, convert them into free carriers, and extract these carriers towards the Si readout channels. The photodetector properties are determined by the fundamental properties of the QDs, in particular their size, their surface passivation and the charge-carrier transport properties between QDs.
The purpose of this PhD is to research the fundamental limits and optimize quantum dot materials and layers for photodetector applications. The materials are deposited from solution. Different core-shell QDs will be evaluated for their absorption window and surface recombination properties. Processing techniques will be optimized to maximize the carrier extraction efficiency. Specifically, ligand exchange processes will be explored, both in solution as well as in thin-film, to reduce the inter-QD spacing and thus improve the charge carrier mobility in film. The most promising material layers will be employed in a p-n junction based photodetector. The PhD student will be involved in the entire fabrication cycle, performed in the state-of-the-art facilities including imec's cleanroom and dedicated thin-film labs.
Required background: chemistry or materials science with strong affinity for device physics
Type of work: 15% literature study, 10% modeling, 10% design, 45% processing, 20% characterization
Supervisor: Paul Heremans
Daily advisors: David Cheyns, Pawel Malinowski
The reference code for this PhD position is SE1712-01. Mention this reference code on your application form.