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Strong absorption and ultrafast localisation in NaBiS2 nanocrystals with slow charge-carrier recombination.

Published version
Peer-reviewed

Type

Article

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Authors

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.

Description

Keywords

51 Physical Sciences, 34 Chemical Sciences, 3406 Physical Chemistry

Journal Title

Nat Commun

Conference Name

Journal ISSN

2041-1723
2041-1723

Volume Title

13

Publisher

Springer Science and Business Media LLC
Sponsorship
Engineering and Physical Sciences Research Council (EP/L016087/1)
European Research Council (756962)
Engineering and Physical Sciences Research Council (EP/R023980/1)
Engineering and Physical Sciences Research Council (EP/S030638/1)
Engineering and Physical Sciences Research Council (EP/R00661X/1)
EPSRC (1951140)