Journal
NANO LETTERS
Volume 19, Issue 3, Pages 1931-1937Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.8b05104
Keywords
Perovskite nanocrystals; ytterbium doping; anion exchange; quantum cutting
Categories
Funding
- National Science Foundation (NSF) through the UW Molecular Engineering Materials Center, a Materials Research Science and Engineering Center [DMR-1719797]
- Washington Research Foundation
- NSF [ECC-1542101]
- University of Washington
- Molecular Engineering and Sciences Institute
- Clean Energy Institute
- National Institutes of Health
- [DMR-1807394]
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Colloidal halide perovskite nanocrystals of CsPbCl3 doped with Yb3+ have demonstrated remarkably high sensitized photoluminescence quantum yields (PLQYs), approaching 200%, attributed to a picosecond quantum-cutting process in which one photon absorbed by the nanocrystal generates two photons emitted by the Yb3+ dopants. This quantum-cutting process is thought to involve a charge-neutral defect cluster within the nanocrystals internal volume. We demonstrate that Yb3+-doped CsPbCl3 nanocrystals can be converted postsynthetically to Yb3+-doped CsPb(Cl1-xBrx)(3) nanocrystals without compromising the desired high PLQYs. Nanocrystal energy gaps can be tuned continuously from E-g approximate to 3.06 eV (405 nm) in CsPbCl3 down to E-g approximate to 2.53 eV (similar to 490 nm) in CsPb(Cl0.25Br0.75)(3) while retaining a constant PLQY above 100%. Reducing E-g further causes a rapid drop in PLQY, interpreted as reflecting an energy threshold for quantum cutting at approximately twice the energy of the Yb3+ F-2(7/2) -> F-2(5/2) absorption threshold. These data demonstrate that very high quantum-cutting energy efficiencies can be achieved in Yb3+-doped CsPb(Cl1-xBrx)(3) nanocrystals, offering the possibility to circumvent thermalization losses in conventional solar technologies. The presence of water during anion exchange is found to have a deleterious effect on the Yb3+ PLQYs but does not affect the nanocrystal shapes or morphologies, or even reduce the excitonic PLQYs of analogous undoped CsPb(Cl1-xBrx)(3) nanocrystals. These results provide valuable information relevant to the development and application of these unique materials for spectral-shifting solar energy conversion technologies.
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