All-inorganic perovskite (CsPbX ${}_{\mathrm{3}}$) nanocrystals (NCs) have recently been widely investigated as versatile solution-processable light-emitting materials. Due to its wide-bandgap nature, the all-inorganic perovskite NC Light-Emitting Diode (LED) is limited to the visible region (400–700 nm). A particularly difficult challenge lies in the practical application of perovskite NCs in the infrared-spectrum region. In this work, a 980 nm NIR all-inorganic perovskite NC LED is demonstrated, which is based on an efficient energy transfer from wide-bandgap materials (CsPbCl ${}_{\mathrm{3}}$ NCs) to ytterbium ions (Yb ${}^{\mathrm{3}\mathrm{+}}$) as an NIR emitter doped in perovskite NCs. The optimized CsPbCl ${}_{\mathrm{3}}$ NC with 15 mol%Yb ${}^{\mathrm{3}\mathrm{+}}$ doping concentration has the strongest 980 nm photoluminescence (PL) peak, with a PL quantum yield of 63%. An inverted perovskite NC LED is fabricated with the structure of ITO/PEDOT: PSS/poly-TPD/CsPbCl ${}_{\mathrm{3}}$:15 mol%Yb ${}^{\mathrm{3}\mathrm{+}}$ NCs/TPBi/LiF/Al. The LED has an External Quantum Efficiency (EQE) of 0.2%, a Full Width at Half Maximum (FWHM) of 47 nm, and a maximum luminescence of 182 cd/m ${}^{\mathrm{2}}$. The introduction of Yb ${}^{\mathrm{3}\mathrm{+}}$ doping in perovskite NCs makes it possible to expand its working wavelength to near-infrared band for next-generation light sources and shows potential applications for optoelectronic integration.

Green Perovskite Light-Emitting Diodes (PeLEDs) have attracted wide attention for full spectrum displays. However, the inferior film morphology and luminescence property of quasi-two-dimensional (quasi-2D) perovskite layers limit the photoelectric property of the PeLEDs. In this paper, the effect of strontium (Sr) doped in quasi-2D perovskite layers is investigated to obtain a high-quality active layer. The morphologies and optical properties of Sr-doped quasi-2D perovskite films with different concentrations are studied. With the addition of strontium, more low-dimensional-layer perovskite phases ( $n\mathrm{=}\mathrm{2}$ and $n\mathrm{=}\mathrm{3}$) appear in quasi-2D perovskite films, providing efficient intraband carrier funneling pathway and facilitating radiative recombination. The photoluminescence (PL) peak intensity of optimized Sr-doped quasi-2D perovskite layers increases 50% compared with the non-strontium counterpart. Moreover, green PeLEDs based on a Sr-doped quasi-2D perovskite layer reach a maximum luminance ( $L_{\max }$) of 2943.77 cd/m ${}^{\mathrm{2}}$, which is three times of the control device. The electroluminescence (EL) peaks of Maximum External Quantum Efficiency (MEQE) and $L_{\max }$ of Sr-doped PeLEDs exhibite a slight shift, indicating the excellent stability and performance of Sr-doped devices. The optimized device can continuously operate for 360 s at MEQE driving voltage, resulting in a half-lifetime of $\mathrm{\sim }$60 s, which is 3-fold greater than that of the control PeLEDs.

In recent years, Perovskite Light-Emitting Diodes (PeLEDs) have received considerable attention in academia. However, with the development of PeLEDs, commercial applications of full-color PeLED technology are largely limited by the progress of blue-emitting devices, due to the uncontrollably accurate composition, unstable properties, and low luminance. In this article, we add Cesium chloride (CsCl) to the quasi-two-dimensional (quasi-2D) perovskite precursor solution and achieve the relatively blue shifts of PeLED emission peak by introducing chloride ions for photoluminescence (PL) and electroluminescence (EL). We also found that the introduction of chlorine ions can make quasi-2D perovskite films thinner with smoother surface of 0.408 nm. It is interesting that the EL peaks and intensities of PeLED are adjustable under different driving voltages in high concentration chlorine-added perovskite devices, and different processes of photo-excited, photo-quenched, and photo-excited occur sequentially with the increasing driving voltage. Our work provides a path for demonstrating full-color screens in the future.