Impurity doping is an effective approach to tuning the optoelectronic performance of host materials by imparting extrinsic electronic channels. Herein, a family of lanthanide (Ln3+) ions was successfully incorporated into a Bi:Cs2AgInCl6 lead-free double-perovskite (DP) semiconductor, expanding the spectral range from visible (Vis) to near-infrared (NIR) and improving the photoluminescence quantum yield (PLQY). After multidoping with Nd, Yb, Er and Tm, Bi/Ln:Cs2AgInCl6 yielded an ultrabroadband continuous emission spectrum with a full width at half-maximum of ~365 nm originating from intrinsic self-trapped exciton recombination and abundant 4f–4f transitions of the Ln3+ dopants. Steady-state and transient-state spectra were used to ascertain the energy transfer and emissive processes. To avoid adverse energy interactions between the various Ln3+ ions in a single DP host, a heterogeneous architecture was designed to spatially confine different Ln3+ dopants via a “DP-in-glass composite” (DiG) structure. This bottom-up strategy endowed the prepared Ln3+-doped DIG with a high PLQY of 40% (nearly three times as high as that of the multidoped DP) and superior long-term stability. Finally, a compact Vis–NIR ultrabroadband (400~2000 nm) light source was easily fabricated by coupling the DiG with a commercial UV LED chip, and this light source has promising applications in nondestructive spectroscopic analyses and multifunctional lighting.
Exploring highly efficient near-infrared (NIR) emitting materials is desirable for the advancement of next-generation smart NIR light sources. Different from most reported Cr3+-doped emitters with far-red emissions, Yb3+-activated phosphors are expected to yield pure NIR (∼1000 nm) light. Herein, a new hot-injection route using all metal-oleate salts to fabricate Yb3+-doped CsPbCl3 perovskite nanocrystals (PeNCs) is reported for the first time, which produce PeNC-sensitized Yb3+ NIR emission with photoluminescence quantum yields (PLQYs) higher than 100%. With the help of temperature-dependent PL spectra, femtosecond transient absorption spectra, and time-resolved PL spectra, it is evidenced that the in situ produced intrinsic shallow trap states in a CsPbCl3 host play a key role in facilitating the picosecond nonradiative cooperative energy transfer from PeNCs to two Yb3+ dopants simultaneously. Using the optimized Yb3+:CsPbCl3 quantum cutters, a phosphor-converted NIR light-emitting diode (pc-NIR-LED) is fabricated, exhibiting an external quantum efficiency of 2%@28 mA, a high NIR output irradiance of 112 mW/cm2@400 mA, and excellent long-term stability. Finally, the designed pc-NIR-LED is demonstrated to have great potential as an invisible night-vision light source.
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