Research Fellows Directory
Dr Daniel Credgington
University of Cambridge
I am working to create cheap, flexible light emitting diodes (LEDs) made from plastics. These have huge potential as a successor to current lighting and display technologies since they can convert electrical energy directly to visible light, without waste, and can be assembled as easily as printing ink on a newspaper.
However, plastic devices have a problem, because the electrons within them (and the positively charged "holes" they leave behind) have a quantum-mechanical property called "spin" that controls how they interact with one another. Similar to positive and negative charge, spin can be either "up" or "down", and in a plastic LED, only electrons and holes with opposite spins can annihilate to give out a photon of light. Meetings between electrons and holes with this "singlet" spin combination only happen about 25% of the time, most have the wrong combination and form entities called "triplets", which cannot emit light and represent huge amounts of wasted electrical energy.
This problem is particularly difficult to crack for materials that emit blue light, which are critical for making white light and full-colour displays. My research explores novel ways of circumventing the limit imposed by spin, either by finding ways to recycle the wasted triplets or by using entirely new light-emitting materials.
Beyond LEDs, I’m also working in the closely-related field of plastic solar cells, which share much of the same physics. I’m also studying new electrode materials which can be incorporated into complete devices, and particularly those suitable for large-scale production.