Perovskite nanocrystals (PeNCs) have emerged as a promising class of luminescent materials offering size and composition-tunable luminescence with high efficiency and color purity in the visible range. PeNCs doped with Yb³⁺ ions, known for their near-infrared (NIR) emission properties, have gained significant attention due to their potential applications. However, these materials still face challenges with weak NIR electroluminescence (EL) emission and low external quantum efficiency (EQE), primarily due to undesired resonance energy transfer (RET) occurring between the host and Yb³⁺ ions, which adversely affects their emission efficiency and device performance. Herein, we report the synergistic enhancement of NIR emission in a CsPbCl₃ host through co-doping with Yb³⁺/Nd³⁺ ions for perovskite LEDs (PeLEDs). The co-doping of Yb³⁺/Nd³⁺ ions in a CsPbCl₃ host resulted in enhanced NIR emission above 1000 nm, which is highly desirable for NIR optoelectronic applications. This cooperative energy transfer between Yb³⁺ and Nd³⁺ can enhance the overall efficiency of energy conversion. Furthermore, the PeLEDs incorporating the co-doped CsPbCl₃/Yb³⁺/Nd³⁺ PeNCs as an emitting layer exhibited significantly enhanced NIR EL compared to the single doped PeLEDs. The optimized co-doped PeLEDs showed improved device performance, including increased EQE of 6.2% at 1035 nm wavelength and low turn-on voltage. Our findings highlight the potential of co-doping with Yb³⁺ and Nd³⁺ ions as a strategy for achieving synergistic enhancement of NIR emission in CsPbCl₃ perovskite materials, which could pave the way for the development of highly efficient perovskite LEDs for NIR optoelectronic applications.

The persistent operational instability of all-inorganic cesium lead halide (CsPbX₃) perovskite nanocrystals (NCs) has hindered their integration into white-light-emitting diodes (WLEDs). This study introduces a transformative approach by engineering a phase transition from CsPbBr₃ NCs to zirconium bromide (ZrBr₄)-stabilized hexagonal nanocomposites (HNs) through a modified hot-injection synthesis. Structural analyses revealed that the ZrBr₄-mediated phase transformation induced a structurally ordered lattice with minimized defects, significantly enhancing charge carrier confinement and radiative recombination efficiency. The resulting HNs achieved an exceptional photoluminescence quantum yield (PLQY) of 92%, prolonged emission lifetimes, and suppressed nonradiative decay, attributed to effective surface passivation. The WLEDs with HNs enabled a breakthrough luminous efficiency of 158 lm/W and a record color rendering index (CRI) of 98, outperforming conventional CsPbX₃-based devices. The WLEDs exhibited robust thermal stability, retaining over 80% of initial emission intensity at 100 °C, and demonstrated exceptional operational stability with negligible PL degradation during 50 h of continuous operation at 100 mA. Commission Internationale de l’Éclairage (CIE) coordinates of (0.35, 0.32) validated pure white-light emission with high chromatic fidelity. This work establishes ZrBr₄-mediated HNs as a paradigm-shifting material platform, addressing critical stability and efficiency challenges in perovskite optoelectronics and paving the way for next-generation, high-performance lighting solutions.

For the first time, to the best of our knowledge, we experimentally demonstrated the new scheme for a coated Plano-convex lens (CPCL) fiber with a maximum coupling efficiency \((\eta\)_max). In the single-mode solid core fiber (SMSCF), the fiber coupling efficiency is ~ 68% injected pump power 632.8 nm (1.5-dB loss was measure with a laser diode) which is difficult to achieve by using conventional technology, and also we reported, without fiber tapering technology has been used to realize low loss coupling from CPCL to SMSCF at low power level, and compare with published data. This is very useful for implementing all optical fiber systems. In addition, it also investigates the effect of bending the output power and beam profile of SMSCF. The Gaussian-like output beam profile is maintained up to \(\cong 7cm\) bending radius. The output mode field with good beam quality shows the mode filtering characteristics of SMSCF. Finally, the result of the fiber coupling efficiency (FCE) illustrates that the scheme of the lens coupling system is the most sensitive scheme to the misalignment and the lensing scheme is the least sensitive to misalignment.