Journal
NATURE COMMUNICATIONS
Volume 13, Issue 1, Pages -Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41467-022-32669-3
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Categories
Funding
- Ministry of Education, Taiwan
- Downing College Cambridge
- Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training in the Advanced Characterisation of Materials (CDT-ACM) [EP/S023259/1]
- EPSRC [EP/L000202, EP/R029431, EP/T022213, EP/N01572X/1, EP/R023980/1, EP/S030638/1, EP/V010840/1]
- ARCHER2 UK National Supercomputing Service
- UK Materials and Molecular Modelling (MMM) Hub (Young) [EP/T022213]
- Technical University of Munich's Institute for Advanced Study - German Excellence Initiative
- Polish National Agency for Academic Exchange within the Bekker programme [PPN/BEK/2020/1/00264/U/00001]
- AiF project [ZIMKK5085302DF0]
- Royal Society Te Aparangi
- Cambridge Commonwealth European and International Trust
- Henry Royce Institut, which the VXSF Facilities within the Bragg Centre for Materials Research at Leeds [EP/P022464/1, EP/R00661X/1]
- EU [824096]
- EPSRC Centre for Doctoral Training in Graphene Technology [EP/L016087/1]
- European Research Council, ERC [758345]
- Royal Society and Tata Group [UF150033]
- European Research Council (ERC) under the European Union [756962]
- Royal Academy of Engineering through the Research Fellowship scheme [RF \201718\1701]
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Ternary chalcogenides such as NaBiS2 are promising materials for solar energy applications. This study reveals the importance of cation disorder in achieving high absorption strength and unusual charge-carrier kinetics in NaBiS2 nanocrystals.
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 >10(5) 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. Ternary chalcogenides are gaining interest as nontoxic, stable solar absorbers. Here, the authors investigate NaBiS2, finding cation disorder to be a critical parameter that enables its high absorption strength and unusual charge-carrier kinetics.
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