Abstract
I-V-VI2 ternary chalcogenides are gaining attention as earth-abundant, nontoxic, and air-stable absorbers for photovoltaic applications. However, the semiconductors explored thus far have slowly-rising absorption onsets, and their charge-carrier transport is not well understood yet. Herein, we investigate cation-disordered NaBiS2 nanocrystals, which have a steep absorption onset, with absorption coefficients reaching >105 cm−1 just above its pseudo-direct bandgap of 1.4 eV. Surprisingly, we also observe an ultrafast (picosecond-time scale) photoconductivity decay and long-lived charge-carrier population persisting for over one microsecond in NaBiS2 nanocrystals. These unusual features arise because of the localised, non-bonding S p character of the upper valence band, which leads to a high density of electronic states at the band edges, ultrafast localisation of spatially-separated electrons and holes, as well as the slow decay of trapped holes. This work reveals the critical role of cation disorder in these systems on both absorption characteristics and charge-carrier kinetics.
| Original language | English |
|---|---|
| Article number | 4960 |
| Journal | Nature Communications |
| Volume | 13 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2022 |
Bibliographical note
Funding Information:The authors would like to thank Laura Spies and Yanhao Wang for their contributions in the early-stage development of NaBiS NCs, and Sachin R. Rondiya, Yuchen Fu, and Kavya Reddy Dudipala for helpful discussions. Y.-T.H. would like to thank funding from the Ministry of Education, Taiwan as well as Downing College Cambridge. S.R.K. acknowledges the Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training in the Advanced Characterisation of Materials (CDT-ACM) (no. EP/S023259/1) for funding a PhD studentship, as well as the UCL Kathleen High Performance Computing Facility (Kathleen@UCL), the Imperial College Research Computing Service and associated support services. By the membership of the UK’s HEC Materials Chemistry Consortium, which is funded by EPSRC (no. EP/L000202, EP/R029431 and EP/T022213), this work used the ARCHER2 UK National Supercomputing Service and the UK Materials and Molecular Modelling (MMM) Hub (Young; EPSRC no. EP/T022213). L.M.H. and M.R. thank EPSRC for funding (no. EP/V010840/1). L.M.H. acknowledges support through a Hans Fischer Senior Fellowship from the Technical University of Munich’s Institute for Advanced Study, funded by the German Excellence Initiative. S.J.Z. acknowledges support from the Polish National Agency for Academic Exchange within the Bekker programme (grant no. PPN/BEK/2020/1/00264/U/00001). I.L. acknowledges the AiF project (ZIM-KK5085302DF0) for financial support. A.J.S would like to thank the Royal Society Te Apārangi and the Cambridge Commonwealth European and International Trust for their financial support. A.J.B. acknowledges support from the Henry Royce Institute (EPSRC grants: EP/P022464/1, EP/R00661X/1), which funded the VXSF Facilities within the Bragg Centre for Materials Research at Leeds ( https://engineering.leeds.ac.uk/vxsf ). The ToF-ERDA measurements and analysis were supported by the RADIATE project under the Grant Agreement 824096 from the EU Research and Innovation programme HORIZON 2020. K.Z. would like to acknowledge the EPSRC Centre for Doctoral Training in Graphene Technology (no. EP/L016087/1) for studentship. D.O.S. acknowledges support from EPSRC (no. EP/N01572X/1) and the European Research Council, ERC (no. 758345). S.D.S. acknowledges support from the Royal Society and Tata Group (no. UF150033), EPSRC (no. EP/R023980/1 and EP/S030638/1) and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (HYPERION, no. 756962). A.R. acknowledges support from EPSRC. R.L.Z.H. would like to thank the Royal Academy of Engineering through the Research Fellowship scheme (no. RF\201718\1701) and EPSRC (no. EP/V014498/1). 2
Funding Information:
The authors would like to thank Laura Spies and Yanhao Wang for their contributions in the early-stage development of NaBiS2 NCs, and Sachin R. Rondiya, Yuchen Fu, and Kavya Reddy Dudipala for helpful discussions. Y.-T.H. would like to thank funding from the Ministry of Education, Taiwan as well as Downing College Cambridge. S.R.K. acknowledges the Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training in the Advanced Characterisation of Materials (CDT-ACM) (no. EP/S023259/1) for funding a PhD studentship, as well as the UCL Kathleen High Performance Computing Facility (Kathleen@UCL), the Imperial College Research Computing Service and associated support services. By the membership of the UK’s HEC Materials Chemistry Consortium, which is funded by EPSRC (no. EP/L000202, EP/R029431 and EP/T022213), this work used the ARCHER2 UK National Supercomputing Service and the UK Materials and Molecular Modelling (MMM) Hub (Young; EPSRC no. EP/T022213). L.M.H. and M.R. thank EPSRC for funding (no. EP/V010840/1). L.M.H. acknowledges support through a Hans Fischer Senior Fellowship from the Technical University of Munich’s Institute for Advanced Study, funded by the German Excellence Initiative. S.J.Z. acknowledges support from the Polish National Agency for Academic Exchange within the Bekker programme (grant no. PPN/BEK/2020/1/00264/U/00001). I.L. acknowledges the AiF project (ZIM-KK5085302DF0) for financial support. A.J.S would like to thank the Royal Society Te Apārangi and the Cambridge Commonwealth European and International Trust for their financial support. A.J.B. acknowledges support from the Henry Royce Institute (EPSRC grants: EP/P022464/1, EP/R00661X/1), which funded the VXSF Facilities within the Bragg Centre for Materials Research at Leeds (https://engineering.leeds.ac.uk/vxsf). The ToF-ERDA measurements and analysis were supported by the RADIATE project under the Grant Agreement 824096 from the EU Research and Innovation programme HORIZON 2020. K.Z. would like to acknowledge the EPSRC Centre for Doctoral Training in Graphene Technology (no. EP/L016087/1) for studentship. D.O.S. acknowledges support from EPSRC (no. EP/N01572X/1) and the European Research Council, ERC (no. 758345). S.D.S. acknowledges support from the Royal Society and Tata Group (no. UF150033), EPSRC (no. EP/R023980/1 and EP/S030638/1) and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (HYPERION, no. 756962). A.R. acknowledges support from EPSRC. R.L.Z.H. would like to thank the Royal Academy of Engineering through the Research Fellowship scheme (no. RF\201718\1701) and EPSRC (no. EP/V014498/1).
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© 2022, The Author(s).