Ytterbium-Doped CsPbCl Quantum Cutters for Near-Infrared Light-Emitting Diodes.

Exploring highly efficient near-infrared (NIR) emitting materials is desirable for the advancement of next-generation smart NIR light sources. Different from most reported Cr-doped emitters with far-red emissions, Yb-activated phosphors are expected to yield pure NIR (∼1000 nm) light. Herein, a new hot-injection route using all metal-oleate salts to fabricate Yb-doped CsPbCl perovskite nanocrystals (PeNCs) is reported for the first time, which produce PeNC-sensitized Yb 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 CsPbCl host play a key role in facilitating the picosecond nonradiative cooperative energy transfer from PeNCs to two Yb dopants simultaneously. Using the optimized Yb:CsPbCl 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/cm@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.