Research and Publications

For a full list of my publications please go to my google scholar page. 

Two-dimensional materials for optical quantum technologies.

Optically-addressable single electronic spins are an important resource for quantum technologies. Specifically, quantum optical networks and nanoscale quantum sensing. Quantum networks are a distribution of quantum states and entanglement between any two points on the globe, that are proposed to enable efficient and secure global communication. Nanoscale quantum sensors implement single electronic spins to detect local magnetic and electronic fields with 10's of nm spatial precision. A major challenge across both areas is identifying spin-photon interfaces with the necessary spin and optical properties that can be integrated to scalable devices. In my research I study new two-dimensional material platforms that emit single photons with favourable properties, and therefore offer a new possibilities for future quantum devices. 

A quantum coherent spin in a two-dimensional material at room temperature. H.L Stern*, C. M. Gilardoni*, Q. Gu, S. Eizagirre Barker, O. Powell, X. Deng, L. Follet, C. Li, A. Ramsey, H. H. Tan, I. Aharonovich and M. Ataure. Nature Materials, accepted (2024).


Room-temperature optically detected magnetic resonance of single defects in hexagonal boron nitride , H.L Stern*, Q. Gu *, J. Jarman*, S. Eizagirre Barker, N. Mendelson, D. Chugh, S. Schott, H. H. Tan, H. Sirringhaus, I. Aharonovich and M. Atature.  Nature Communications, 13, 681, (2022).


'Two-dimensional material could store quantum information at room temperature.' Cambridge University Research News

Spectrally resolved photodynamics of individual emitters in large-area monolayers of hexagonal Boron Nitride, H.L. Stern, R. Wang, R. Mizuta, J.C. Stewart, T. D. Roberts, R. Wai, N. S. Ginsberg, D. Klenerman, S. Hofmann and S. Lee. ACS Nano, 13, 4538-4547, (2019).

Molecular materials for solar energy conversion.

Carbon-based molecular semiconductors are materials that can efficiently absorb solar photons to generate free charges. This makes these materials exciting candidates for use in solar cells, as they are solution-processable, affordable and tuneable.  In addition,  a class of these materials offers ways of boosting solar cell efficiencies beyond theoretical limits (Shockley Queisser limit) - via an ultrafast process that converts one photo-generated spin singlet exciton  to two spin triplet excitons (single exciton fission).  During my PhD, I showed how singlet exciton fission can proceed, even when the energy of the two spin triplet excitons is greater than the energy of the absorbed photon, ie. endothermic.  Using a combination of ultrafast transient absorption and photoluminescence spectroscopies my research identified a critical intermediate excited state in solution and the solid state .

Elusive excited states identified from cutting-edge molecular movies. A. Musser and H. L. Stern. Nature, News and Views, 2023. 


Vibronically coherent ultrafast triplet-pair formation and subsequent thermally activated dissociation control efficient endothermic singlet fission. H.L Stern, A. Cheminal, S. R Yost, K. Broch, S.L. Bayliss, K. Chen, M. Tabachyk, K. Thorley, N. Greenham, J. M Hodgkiss, J. Anthony, M. Head-Gordon, A.J Musser, A. Rao and R. H. Friend. Nature Chemistry, 9, 1205-1212 (2017). 

Elucidation of excitation energy dependent correlated triplet pair formation pathways in an endothermic singlet fission system. A. Thampi, H.L. Stern, A. Cheminal, M. J.Y. Tayebjee, A.J. Petty, J.E. Anthony and A. Rao. JACS, 140,13 (2017). 

Synthesis and exciton dynamics of donor-orthogonal acceptor conjugated polymers: Reducing the singlet–triplet energy gap. D.M.E. Freeman, A.J. Musser, J.M. Frost, H.L. Stern, A.K. Forster, K. J. Fallon, A.G. Rapidis, F. Cacialli, I. McCulloch, T.M. Clarke, R.H Friend and H. Bronstein. JACS, 139, 11073-11080 (2017),

Limits for Recombination in a Low Energy Loss Organic Heterojunction. S. M. Menke, A. Sadhanala, M. Nikolka, N. A. Ran, M. K. Ravva, S. Abdel-Azeim, H. L. Stern, M. Wang, H. Sirringhaus, T.Q. Nguyen, J.L. Brédas, G. C. Bazan and R. H. Friend. ACS Nano, 10,12 (2016).

Identification of a triplet pair intermediate in singlet exciton fission in solution. H.L. Stern, A.J. Musser, S. Gelinas, P. Parkinson, L. M. Herz, M. J. Bruzek, J. Anthony, R. H. Friend, and B.J. Walker, PNAS,  111, 25 (2015).

Book Chapters

Singlet exciton fission in solutionH.L. Stern, A.J. Musser and R.H. Friend. Photochemistry, 43. (2015). 

Patents

GB2579061 - Field-effect transistor for sensing target molecules