1. Tetrafluoroborate-Induced Reduction in Defect Density in Hybrid Perovskites through Halide Management
- Author
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Nagane, S, Hope, Mic, Kubicki, D, Li, Weiwei, Verma, S, Ferrer Orri, Jordi, Chiang, Y, Driscoll, J, Grey, Clare, Stranks, Samuel, Nagane, Satyawan [0000-0002-1146-4754], Kubicki, Dominik [0000-0002-9231-6779], Ferrer Orri, Jordi [0000-0002-0432-5932], Driscoll, Judith [0000-0003-4987-6620], Grey, Clare [0000-0001-5572-192X], Stranks, Samuel [0000-0002-8303-7292], and Apollo - University of Cambridge Repository
- Subjects
charge-carrier recombination ,tetrafluoroborate ,photoluminescence ,surface treatment ,perovskite solar cells ,defects - Abstract
Hybrid perovskite-based optoelectronic devices are demonstrating unprecedented growth in performance, and defect passivation approaches are highly promising routes to further improve properties. Here, the effect of the molecular ion BF4-, introduced via methylammonium tetrafluoroborate (MABF4) in a surface treatment for MAPbI3 perovskite is reported. The optical spectroscopic characterisations shows that the introduction of tetrafluoroborate leads to reduced non-radiative charge carrier recombination with a reduction in first order recombination rate from 6.5 × 106 to 2.5 × 105 s-1 in BF4--treated samples, and a consequent increase in photoluminescence quantum yield by an order of magnitude (from 0.5% to 10.4%). 19F, 11B and 14N solid-state NMR is used to elucidate the atomic-level mechanism of the BF4- additive-induced improvements, revealing that the BF4- acts as a scavenger of excess MAI by forming MAI–MABF4 cocrystals. This shifts the equilibrium of iodide concentration in the perovskite phase is presumably due to the formation of MAI-MABF4 cocrystal, thereby reducing the concentration of interstitial iodide defects that act as deep traps and non-radiative recombination centers. These collective results allow us, for the first time, to elucidate the microscopic mechanism of action of BF4-.
- Published
- 2021
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