30 November 2016

Durham University researchers Dr. Marc Etherington, Dr. Heather Higginbotham, and Prof. Andrew Monkman have recently published the paper “Revealing the spin–vibronic coupling mechanism of thermally activated delayed fluorescence” in the prestigious, high-impact journal Nature Communications.

In the paper, the researchers propose that knowing the underlying photophysics of thermally-activated delay fluorescence (TADF) can enable proper design of high efficiency organic light emitting diodes. They define a model to describe reverse intersystem crossing (rISC) in donor-acceptor charge-transfer molecules, where spin orbit coupling between singlet and triplet states is mediated by one of the local triplet states of donor (or acceptor). This second order, vibronically coupled mechanism describes the basic photophysics of TADF. In a series of measurements whereby the energy ordering of the charge transfer (CT) excited states and the local triplet are tuned in and out of resonance, the researchers show that TADF reaches a maximum at the resonance point, substantiating their model of rISC. Moreover, using photoinduced absorption, the researchers show how the populations of both singlet and triplet CT states and the local triplet state change in and out of resonance. Their vibronic coupling rISC model is used to predict this behaviour and describes how rISC and TADF are affected by external perturbation.

Their research was undertaken together with Newcastle University researchers Jamie Gibson and Dr. Thomas Penfold and supported with funding from the PHEBE project.

To read the full paper, please visit the Nature Communication’s website here.

About Durham University

Durham University is a world top 100 university with a global reputation and performance in research and education. It is a member of the Russell Group of leading research-intensive UK universities. Research at Durham shapes local, national and international agendas, and directly informs the teaching of our students. It was ranked in the world top 25 for the employability of its students by blue-chip companies world-wide (QS World University Rankings 2014/15) and in the global top 50 for Arts and Humanities (THE World University Rankings 2013/14). In the 2015 Complete University Guide, Durham was the only UK university to receive a top ten ranking for all of its subjects and 19 of Durham’s 22 subjects were ranked in the top five. Furthermore, Durham was named as The Times and Sunday Times 'Sports University of the Year 2015' in recognition of outstanding performance in both the research and teaching of sport, and student and community participation in sport at all levels.

About PHEBE Project

Exploiting ground-breaking research in the field of thermally activated delayed fluorescence (TADF), the €4M PHEBE project aims to develop innovative, high-efficiency, blue emitters for white organic light emitting diodes (OLEDs). While OLEDs are already an efficient and resource-saving illumination system, the new emitters are expected to significantly enhance their cost performance and environmental-friendliness. The PHEBE project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement number 641725. It started on 1st February 2015 and will run for 3 years.