Recently, the research group of Professor Liangsheng Liao from Soochow University and their collaborators published a paper entitled "Efficient Near-Infrared Electroluminescence from Lanthanide-Doped Perovskite Quantum Cutters" on Angew. Chem. Int. Ed.
The paper demonstrates a highly efficient near-infrared LED with a peak EQE of 7.7% at a central wavelength of 990 nm, representing the most efficient perovskite-based LEDs with emission wavelengths beyond 850 nm.
Introduction
Perovskite nanocrystals (PeNCs) exhibit size- and composition-tunable luminescence with high efficiency and high color purity in visible light. However, obtaining efficient electroluminescence (EL) in the near-infrared (NIR) region is challenging, limiting its potential applications.
Here, we demonstrate a highly efficient near-infrared light-emitting diode (LED) that extends the EL wavelength to 1000 nm by doping ytterbium ions into the PeNC matrix (Yb3+: PeNCs), which is directly sensitized by the PeNC matrix. Yb3+ ion to achieve. The efficient quantum tailoring process enables Yb3+:PeNCs to achieve photoluminescence quantum yields (PLQYs) as high as 126%.
Using halide composition engineering and surface passivation strategies to improve PLQY and charge transport balance, we demonstrate a highly efficient near-infrared LED with a peak EQE of 7.7% at a central wavelength of 990 nm, representing the highest efficiency for emission wavelengths beyond 850 nm. Perovskite-based LEDs.
Innovative point: In this study, we doped ytterbium ions into perovskite nanocrystals to extend the electroluminescence wavelength to 1000 nm. The synergistic effect of halide stoichiometry control and surface passivation enables us to realize highly efficient near-infrared LEDs with a peak EQE of 7.7%, the highest efficiency so far among OLEDs and PeLEDs with peak wavelengths exceeding 850 nm.
Graphic guide
Figure 1 a) TEM image and elemental mapping of Yb3+:PeNCs, the inset of the TEM image shows the crystal diffraction pattern. b) XRD pattern, c) IR PLQY, d) PL spectrum, e) Absorption of different halide stoichiometry of Yb3+:CsPb(Cl1-xBrx)3 PeNCs. f) Yb3+: The energy transfer mechanism of PeNCs, the three recombination pathways are denoted as (1), (2), and (3), respectively. g) TA spectra at selected pump-probe delays. h) Normalized TA signal decay at 450 nm versus time for Yb3+:PeNCs with different nominal doping concentrations.
Fig. 2 a) Schematic diagram of the device structure of near-infrared PeLEDs based on Yb3+: CsPb(Cl1-xBrx)3 NC emitter. b) Energy band diagram. c) Power distribution of the light energy channel inside the near-infrared LED. d) Based on the EQE and J characteristics of PeLEDs of the Yb3+:CsPbCl1-xBrx NC emitter, the EQE is calculated considering only the near-infrared peak. e) PLQY of PeNC films and peak EQE (mean values) of NIR PeLEDs at different excitonic wavelengths. f) EL spectra corresponding to different deviations from 3.2 V to 6 V, with a step size of 0.2V. The inset shows the EL spectrum of the PeLED operated at 3.2 V.
Figure 3a) The inset shows the molecular structure of BTC. b) EQE - current density characteristics. c) Peak EQE histograms of pristine (blue curve) and passivated (red curve) LED devices. J-V curves of hole-only devices d) and electron-only devices e) based on pristine and passivated Yb3+:PeNCs. The black dashed line indicates the trap filling voltage. f) Peak EQE comparison between our devices, previously reported NIR PeLDs and OLEDs (EL peak wavelengths over 850 nm).
Figure 4 a) Surface passivation mechanism of Yb3+: PeNCs. XPS spectra of pristine and passivated Yb3+: Yb 4d; b) XPS spectra of Pb 4f5/2 and 4f7/2 c). d) FTIR transmission spectra of benzyl thiocyanate, pristine and passivated Yb3+: PeNCs. e) Transient PL decay of pristine and passivated Yb3+:PeNCs obtained at a wavelength of 480 nm. f) PLQY of residual exciton emission at 480 nm (blue curve) of PeNCs and PLQY of near-infrared emission of Yb3+ ions at 990 nm (pink curve).
