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Materials Research Institute



MRI Seminar 'Conversion between singlet and triplet states in the strong and weak coupling regimes.' with Dr Karl Börjesson, University of Gothenburg

Image: Dr Karl Börjesson
Dr Karl Börjesson

Date: 25 September 2019   Time: 15:00 - 16:00

We welcome Dr Karl Börjesson from the University of Gothenburg where Karl leads a research group specialising in the construction of molecules or molecular based systems that are able to perform highly specialized functions to be used within material sciences. The competence of the group involves both the synthesis of complex molecules and the photophysical/electrical characterization of the molecular based systems.

Chemists can today synthesize virtually any molecule imaginable. By fine tuning the molecular structure, optimized physical, chemical, or biological properties are routinely achieved. However, even though molecular optimization has reshaped the world we live in, there is always a point at which the laws of physics limit the performance of molecular systems. Tailoring of molecular properties can be achieved through strong coupling between molecular states and the zero-point fluctuations of the electromagnetic field (vacuum field) [1]. The formed hybrid states (exciton polaritons) have unique chemical and physical properties and can be viewed as a linear combination of light (vacuum field) and matter (molecules). I will present how the energy difference between singlet and triplet energy levels can be reduced by strong light matter interactions, allowing for a higher rate of reversed intersystem crossing [2]. I will further describe how resonance energy transfer can be used for multiplicity conversion in the weak coupling regime [3]. The last part of my talk will be on triplet-triplet annihilation photon upconversion, focusing on excimer formation on the triplet surface, which is a previously overlooked process in the community [4].

[1] Hertzog, Wang, Mony and Börjesson, Chem. Soc. Rev., 2019, 48, 937-961.
[2] Stranius, Hertzog and Börjesson, Nat. Commun., 2018, 9:2273.
[3] Cravcenco, Hertzog, Ye, Iqbal, Mueller, Eriksson and Börjesson, Sci. Adv. 2019, accepted
[4] Ye, Gray, Mårtensson and Börjesson, J. Am. Chem. Soc., 2019, 14, 124, 9578-9584.

For more information see group homepage at

Location:  PP1 People's Palace, Mile End Campus, Queen Mary University of London
Contact:  Dr Oliver Fenwick