Understanding ultrafast charge transfer processes in SnS and SnS2: using the core hole clock method to measure attosecond orbital-dependent electron delocalisation in semiconducting layered materials

Freddy E. Oropeza, Mariam Barawi, Elena Alfonso-Gonzalez, Victor A. de la Pena O'Shea, Juan F. Trigo, Cecilia Guillen, Fernan Saiz, Ignacio J. Villar-Garcia

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2 Scopus citations


SnS and SnS2 are earth abundant layered semiconductors that owing to their optoelectronic properties have been proposed as materials for different photovoltaic, photosensing and photocatalytic applications. The intrinsic efficiency of these materials for such applications is driven by their charge transfer dynamics, which in turn depend on their electronic structure and the interaction of the molecular orbitals involved in the charge transfer process. In this publication, we provide a step-by-step description of the use of the core hole clock method to obtain orbital dependent charge transfer times for SnS2 and SnS down to the attosecond time scale. We use both S 1s and Sn 3d core holes, with natural core hole lifetimes of 1.3 fs and 300 as, as time references to obtain a complete picture of electron delocalisation times across the conduction band of both materials. Ultrafast electron delocalisation times, lower than 5 femtoseconds and as low as tens of attoseconds, are measured for electrons excited to the unoccupied molecular orbitals of both materials. SnS delocalisation times are found to be shorter than those for SnS2 for all probed molecular orbitals, with delocalisation times being more than an order of magnitude shorter for higher lying molecular orbitals. DFT calculations show that charge transfer dynamics are strongly influenced by the interlayer interaction within these materials. The slower delocalisation of electrons in SnS2 can be linked to the restricted out of plane spatial dispersion of the molecular orbitals in the conduction band and consequent limitation of the electron delocalisation pathways. The results presented in this paper highlight the high potential of combining the core hole clock method with high-level DFT calculations to study orbital dependent charge transfer in semiconductor materials for optoelectronic applications down to the attosecond scale.
Original languageEnglish (US)
StatePublished - 2021

Bibliographical note

KAUST Repository Item: Exported on 2021-08-12
Acknowledgements: This work was supported by the EU (ERC CoG HyMAP 648319) and Spanish MINECO (PID2019-106315RB-I00). Authors also would like to thank Comunidad de Madrid and European Structural Funds for their financial support for the FotoArt-CM project (S2018/NMT-4367) and Fundacio´n Ramo´n Areces. Mariam Barawi thanks Spanish MINECO–AEI for the Juan de la Cierva Incorporacio´n grant (JC2019 – 042430 – I). The authors would like to thank Diamond Light Source for beamtime (proposals SI21754 and SI22365), and the staff of beamlines
I09 and B07 for assistance, and in particular to Dr Pardeep Kumar Thakur and Dr Federica Venturini for their excellent support as main local contacts. Ignacio J. Villar-Garcia would like to thank Dr Kevin J. R. Lovelock for introducing him, some time ago, to the core hole clock technique and for helpful discussions along the way.

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry


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