PhD Project: Printing of Organic Electronic Displays

Durham University - Department of Chemistry

PhD position in the Department of Chemistry, Durham University

Supervisor: Prof. Colin Bain (Durham)
Co-supervisor: Prof. Stephen Wilson (Strathclyde)
Industrial Sponsor: Merck Ltd.
Industrial Supervisor: Dan Walker

Period: October 2017 – September 2021

Organic light-emitting diodes (OLEDs) are the basis of the technology behind the screens of the Samsung Galaxy mobile phones and the latest ultrathin and curved TVs. Current OLED screens are manufactured by evaporation of the active molecules in a vacuum chamber – an expensive and wasteful process and one that is increasingly difficult to scale to larger substrates. For a long time, printing (and in particular ink-jet printing) has been held out as an alternative manufacturing technology that is cheap, scalable and efficient in its use of the expensive dyes that generate the light in the OLED device. Printing also allows manufacturers to use materials, such as light-emitting polymers, that cannot be evaporated without degradation. The challenge for printing has been to deposit successive layers of organic material (typically four separate layers between the cathode and the anode) with sufficient control of the uniformity, thickness and interfaces to compete with vacuum deposition. One of the underlying issues is that we do not understand how drops of liquid dry in a pixel on a substrate.

This project is a direct continuation of a successful iCase project with Merck Ltd. in Southampton on the drying of solutions of active ingredients on a patterned surface. We established interferometric and particle-tracking techniques to study evaporation of solvents and solvent mixtures and developed hypotheses to explain the drying behaviour and the consequences for the morphology of the deposit of an active material left behind after the solvent evaporates. This understanding allowed us to propose an approach for the deposition of uniform films of controlled thickness of active materials in a display pixel.

This project will develop a predictive model for drop drying based on solvent properties, using a quantitative theoretical model (developed in collaboration with Prof. Stephen Wilson in the Department of Mathematics at Strathclyde University) validated against experimental data obtained at Durham. We will extend the study to the drying conditions employed in manufacturing processes, including vacuum dryers and radiant heaters. We will develop techniques (spectroscopy and microscopy) to measure how the active ingredients precipitate from solution as the solvent evaporates and whether different solutes can be co-deposited in a single printing step. The project will involve both small molecules and polymers as the active ingredients.

The PhD duration is 4 years starting from October 2017 and is jointly supported by the Industrial Strategy Challenge Fund, through the EPSRC, and by Merck Ltd.

Applications will be considered upon receipt and the position will remain open until filled. Applicants should have a 1st class or 2:1 Masters degree or equivalent in chemistry, physics, chemical engineering or a cognate discipline.

Informal enquiries should be sent to c.d.bain@durham.ac.uk

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Type / Role:

PhD

Location(s):

Northern England