RESUMO
Nonlinear absorption of metal-halide perovskite nanocrystals (NCs) makes them an ideal candidate for applications which require multiphoton-excited photoluminescence. By doping perovskite NCs with lanthanides, their emission can be extended into the near-infrared (NIR) spectral region. We demonstrate how the combination of Yb3+ doping and bandgap engineering of cesium lead halide perovskite NCs performed by anion exchange (from Cl- to Br-) leads to efficient and tunable emitters that operate under two-photon excitation in the NIR spectral region. By optimizing the anion composition, Yb3+-doped CsPbClxBr3-x NCs exhibited high values of two-photon absorption cross-section reaching 2.3 × 105 GM, and displayed dual-band emission located both in the visible (407-493 nm) and NIR (985 nm). With a view of practical applications of bio-visualisation in the NIR spectral range, these NCs were embedded into silica microspheres which were further wrapped with amphiphilic polymer shells to ensure their water-compatibility. The resulting microspheres with embedded NCs could be easily dispersed in both toluene and water, while still exhibiting a dual-band emission in visible and NIR under both one- and two-photon excitation conditions.
RESUMO
Lead-halide perovskite nanocrystals are an attractive class of materials since they can be easily fabricated, their optical properties can be tuned all over the visible spectral range, and they possess high emission quantum yields and narrow photoluminescence linewidths. Doping perovskites with lanthanides is one of the ways to widen the spectral range of their emission, making them attractive for further applications. Herein, we summarize the recent progress in the synthesis of ytterbium-doped perovskite nanocrystals in terms of the varying synthesis parameters such as temperature, ligand molar ratio, ytterbium precursor type, and dopant content. We further consider the dependence of morphology (size and ytterbium content) and optical parameters (photoluminescence quantum yield in visible and near-infrared spectral ranges) on the synthesis parameters. The developed open-source code approximates those dependencies as multiple-parameter linear regression and allows us to estimate the value of the photoluminescence quantum yield from the parameters of the perovskite synthesis. Further use and promotion of an open-source database will expand the possibilities of the developed code to predict the synthesis protocols for doped perovskite nanocrystals.
