Engineering Tunable Broadband Near‐Infrared Emission in Transparent Rare‐Earth Doped Nanocrystals‐in‐Glass Composites via a Bottom‐Up Strategy.

Applications of trivalent rare earth (RE3+)‐doped light sources in solid‐state laser technology, optical communications, biolabeling, and solar energy management have stimulated a growing demand for broadband emission with flexible tunability and high efficiency. Codoping is a conventional strategy for manipulating the photoluminescence of active RE3+ ions. However, energy transfer between sensitizers and activators usually induces nonradiative migration depletion that brings detrimental luminescent quenching. Here, a transparent framework is employed to assemble ordered RE3+‐doped emitters to extend the emission spectral range by extracting photons from a variety of RE3+ ions with sequential energy gradient. To block migration‐mediated depletion between different RE3+ ions, a nanoscopic heterogeneous architecture is constructed to spatially confine the RE3+ clusters via a "nanocrystals‐in‐glass composite" (NGC) structure. This bottom‐up strategy endows the obtained RE3+‐doped NGC with high emission intensity (nearly one order of magnitude enhancement) and broadband near‐infrared emission from 1300 to 1600 nm, which covers nearly the whole low‐loss optical communication window. Most crucially, NGC is a versatile approach to design tunable broadband emission for the potential applications in high‐performance photonic devices, which also provides new opportunities for engineering multifunctional materials by integration and manipulation of diverse functional building units in a nanoscopic region. A tunable broadband emission is demonstrated by assembly of ordered rare‐earth‐doped emitters with sequential energy gradient. Migration‐mediated energy quenching has been successfully suppressed by nanoscopic heterogeneous structures constructed in transparent nanocrystals‐in‐glass composites. This assembly strategy highlights the possibility to fabricate multifunctional materials by linking different building units with photonic, magnetic, and electronic properties in a transparent framework. [ABSTRACT FROM AUTHOR]