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Understanding the spin-entangled triplet-pair state in organic semiconductors.

  • Full or part time
  • Application Deadline
    Sunday, March 31, 2019
  • Competition Funded PhD Project (Students Worldwide)
    Competition Funded PhD Project (Students Worldwide)

Project Description

Singlet fission is a process whereby one photon creates two excited states. This two-for-one mechanism could dramatically increase solar cell efficiency (from 33% to >40%). Recently, there has been much academic and industrial interest in developing new singlet fission sensitizers, but to-date no material has proved ideal [1]. This is in part because of a fundamental lack of understanding of the singlet fission process and what molecular parameters control it.

Singlet fission is often described as proceeding through an intermediate state known as (TT): a correlated pair of triplets, with spins that may remain entangled even as the triplets separate (T. . . T) [2,3].

The Triplet-Pair State has only been recently observed experimentally [5] and current quantum mechanical descriptions of triplet-pairs do not agree [2,6]. Recent measurements make clear, however, that the standard model proposed by Merrifield in the 1970s is inadequate. With the standard model no longer applicable, we need to develop a complete new description of triplet-pair states in organic semiconductors.

In this project, you will develop an in-depth understanding of triplet-pair states in organic semiconductors with an aim of developing a new model to describe them. To this end you will study the effect of high (>1T) magnetic field on temperature-dependent and time-resolved triplet-pair emission behavior along with transient absorption spectroscopy under low magnetic field (<1T).

Understanding triplet-pair states will have important consequences for solar cell applications [1] and – because the triplets within the pair remain spin-entangled even as they separate [2] – understanding them could lead to development of new spintronic or quantum devices of the future.

Science Graduate School:
As a PhD student in one of the science departments at the University of Sheffield, you’ll be part of the Science Graduate School – a community of postgraduate researchers working across biology, chemistry, physics, mathematics and psychology. You’ll get access to training opportunities designed to support your career development by helping you gain professional skills that are essential in all areas of science. You’ll be able to learn how to recognise good research and research behaviour, improve your communication abilities and experience technologies that are used in academia, industry and many related careers. Visit to learn more.

Funding Notes

If you submit your application after the 31 March 2019, you will be considered for any remaining funding, but please note all of our funding may be allocated in the first round.


[1] Rao & Friend, Harnessing singlet exciton fission to break the Shockley–Queisser limit Nature Reviews, 2, 17063 (2017);
[2] Scholes, Correlated Pair States Formed by Singlet Fission and Exciton−Exciton Annihilation J. Phys. Chem. A, 119, 12699−12705 (2015);
[3] Teichen & Eaves Collective aspects of singlet fission in molecular crystals. J. Chem. Phys. 143:44118 (2015);
[4] Smith & Michl, Singlet fission. Chemical Reviews 110:6891–6936 (2010);
[5] Yong et al., The entangled triplet pair state in acene and heteroacene materials. Nature Communications 8:15953 (2017);
[6] Kollmar, Electronic structure of diradical and dicarbene intermediates in short-chain polydiacetylene oligomers, J. Chem. Phys. 98, 7210 (1993)

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