Dual-Modal Photon Upconverting and Downshifting Emissions from Ultra-stable CsPbBr Perovskite Nanocrystals Triggered by Co-Growth of Tm:NaYbF Nanocrystals in Glass.

This work reports a novel dual-phase glass containing Tm:NaYbF upconverting nanocrystals (UCNCs) and CsPbBr perovskite nanocrystals (PNCs). The advantages of this kind of nanocomposite are that it provides a solid inorganic glass host for the in situ co-growth of UCNCs and PNCs, and protects PNCs against decomposition affected by the external environment. Tm:NaYbF NC-sensitized stable CsPbBr PNCs photon UC emission in PNCs is achieved under the irradiation of a 980 nm near-infrared (NIR) laser, and the mechanism is evidenced to be radiative energy transfer (ET) from Tm: G state to PNCs rather than nonradiative Förster resonance ET. Consequently, the decay lifetime of exciton recombination is remarkably lengthened from intrinsic nanoseconds to milliseconds since carriers in PNCs are fed from the long-lifetime Tm intermediate state. Under the simultaneous excitation of the ultraviolet (UV) light and NIR laser, dual-modal photon UC and downshifting (DS) emissions from ultra-stable CsPbBr PNCs in the glass are observed, and the combined UC/DS emitting color can be easily altered by modifying the pumping light power. In addition, UC exciton recombination and Tm 4f-4f transitions are found to be highly temperature sensitive. All these unique emissive features enable the practical applications of the developed dual-phase glass in advanced anti-counterfeit and accurate temperature detection.