Negative Thermal Quenching in Quantum-Cutting Yb-Doped CsPb(ClBr) Perovskite Nanocrystals.

Ytterbium-doped all-inorganic lead-halide perovskites (Yb:CsPb(ClBr)) show broadband absorption and exceptionally high near-infrared photoluminescence quantum yields, providing opportunities for solar spectral shaping to improve photovoltaic power conversion efficiencies. Here, we report that Yb:CsPb(ClBr) NCs also show extremely strong negative thermal quenching of the Yb luminescence, with intensities at room temperature >100 times those at 5 K for some compositions. Analysis of this temperature dependence as a function of shows that it stems from thermally activated quantum cutting related to the temperature dependence of the spectral overlap between the PL of the perovskite (donor) and the simultaneous-pair absorption of two Yb ions (acceptor).

Anion Exchange and the Quantum-Cutting Energy Threshold in Ytterbium-Doped CsPb(ClBr ) Perovskite Nanocrystals.

Colloidal halide perovskite nanocrystals of CsPbCl doped with Yb 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 Yb dopants. This quantum-cutting process is thought to involve a charge-neutral defect cluster within the nanocrystal's internal volume. We demonstrate that Yb-doped CsPbCl nanocrystals can be converted postsynthetically to Yb-doped CsPb(ClBr ) nanocrystals without compromising the desired high PLQYs.

Picosecond Quantum Cutting Generates Photoluminescence Quantum Yields Over 100% in Ytterbium-Doped CsPbCl Nanocrystals.

Recent advances in the ytterbium doping of CsPbX (X = Cl or Cl/Br) nanocrystals have presented exciting new opportunities for their application as downconverters in solar-energy-conversion technologies. Here, we describe a hot-injection synthesis of Yb:CsPbCl nanocrystals that reproducibly yields sensitized YbF → F luminescence with near-infrared photoluminescence quantum yields (PLQYs) well over 100% and almost no excitonic luminescence. Near-infrared PLQYs of 170% have been measured.

Flat-Band Potentials of Molecularly Thin Metal Oxide Nanosheets.

Exfoliated nanosheets derived from Dion-Jacobson phase layer perovskites (TBAxH1-xA2B3O10, A = Sr, Ca, B = Nb, Ta) were grown layer-by-layer on fluorine-doped tin oxide and gold electrode surfaces. Electrochemical impedance spectra (EIS) of the five-layer nanosheet films in contact with aqueous electrolyte solutions were analyzed by the Mott-Schottky method to obtain flat-band potentials (VFB) of the oxide semiconductors as a function of pH. Despite capacitive contributions from the electrode-solution interface, reliable values could be obtained from capacitance measurements over a limited potential range near VFB.

Earthworms as paratenic hosts of toxoplasmosis in eastern barred bandicoots in Tasmania.

An experimental feeding study was designed to assess the role of earthworms in the transmission of Toxoplasma gondii infection to eastern barred bandicoots (Perameles gunnii). Six animals with no agglutinating antibodies to T. gondii were fed artificially cultured earthworms that had been maintained in autoclaved nutrient-enriched soil.