Sai Xu

Rare‐earth‐based lead‐free halide perovskite nanocrystals (NCs) are promising for optoelectronics due to their narrow‐band emission and physicochemical stability. However, the intrinsic 4f‐4f forbidden transitions of rare‐earth ions result in limited absorption cross‐sections. Furthermore, inevitable surface defects at the nanoscale trigger non‐radiative recombination, limiting luminescence efficiency. Herein, a surface engineering strategy utilizing fluoroquinolone (FQ) molecules is proposed to construct a hybrid system. Specifically, by introducing norfloxacin (NFLX) as a surface ligand, NFLX‐modified Cs ₃ TbCl ₆ nanocrystals (NCs) have been developed that achieve a near‐unity photoluminescence quantum yield (PLQY) of 99.67%. Experiments and theoretical analyses reveal that the organic ligands effectively passivate surface defects, thereby suppressing non‐radiative transitions. Simultaneously, the ligand acts as an efficient antenna that amplifies excitation light capture and establishes energy transfer pathways to NCs. Notably, it is demonstrated that beyond energy level matching, the electronic effects, steric configurations, and absorption capacities of ligand are crucial factors for efficient antenna effect. Finally, the effectiveness of this strategy is validated through applications in extreme‐environment‐resilient fluorescent anti‐counterfeiting fibers and high‐quality white light‐emitting diodes (WLEDs). This work overcomes the bottleneck limiting the luminescence efficiency of rare‐earth halide NCs, paving a new technical pathway for the design of high‐efficiency surface‐coordinated hybrid rare‐earth luminescent NCs.

Phosphors with efficient blue‐light absorption and near‐infrared (NIR) emission conversion capabilities are essential for high‐performance phosphor‐converted NIR LEDs. Herein, a novel strategy for enhancing blue‐light absorption and Er ³⁺ NIR‐II emission in double perovskites via Mo ⁴⁺ sensitization is developed. Density functional theory calculations reveal that the introduction of Mo ⁴⁺ contributes Mo 4d orbitals to the conduction band minimum (CBM), narrowing the bandgap and enabling strong blue‐light absorption. The large absorption cross‐section of Mo ⁴⁺ effectively overcomes the limitation of narrow 4f‐4f absorption transitions in Er ³⁺ . Under blue light excitation, Mo ⁴⁺ /Er ³⁺ co‐doped Cs ₂ NaBiCl ₆ double perovskite phosphors exhibit broadband emission from Mo ⁴⁺ at ∼900 nm along with intrinsic emissions from Er ³⁺ at ∼1000 nm and ∼1540 nm. Efficient energy transfer from Mo ⁴⁺ to Er ³⁺ boosts the NIR emission at ∼1540 nm by 36.09 times compared to Er ³⁺ single‐doped sample. The optimized phosphor (Cs ₂ NaBiCl ₆ :20%Mo ⁴⁺ /30%Er ³⁺ ) achieves a total NIR‐II PLQY of 68.7%, with 34.8% at ∼1540 nm. Integrated with a commercial blue LED chip, an efficient NIR‐II LED achieving a maximum photoelectric conversion efficiency of 13.26% is demonstrated, highlighting potential in anti‐counterfeiting, non‐destructive inspection, and night vision. These results open a novel pathway for efficient sensitization in blue‐light‐excitable NIR phosphors.

Zero-dimensional (0D) rare-earth-based metal halides show great potential in photonic and optoelectronic applications owing to their high stability, strong exciton confinement, and tunable energy levels. However, the weak absorption and narrow 4f-4f transitions of rare-earth ions limit their performance. To address this, a series of Sb³⁺-doped Cs₃LnCl₆ (Ln: Yb, La, Eu, Ho, Ce, Er, Tb, Sm, Y) nanocrystals were synthesized via a hot-injection method to study the role of Sb³⁺ doping. Sb³⁺ incorporation induces strong broadband self-trapped exciton (STE) emission from Jahn–Teller-distorted [SbCl₆]³⁻ units and enables efficient energy transfer from STEs to rare-earth ions. As a result, the photoluminescence intensity and spectral tunability are improved, accompanied by bandgap narrowing and enhanced light absorption. Different lanthanide hosts exhibit distinct luminescence behaviors: La-based materials show dominant STE emission, while Tb-, Er-, Yb-, Ho-, and Sm-based systems display STE-mediated energy transfer and enhanced f-f emission. In Eu- and Ce-based hosts, unique mechanisms involving Eu²⁺/Eu³⁺ conversion and Ce³⁺ → STE energy transfer are observed. Moreover, composition-dependent emissions in Sb³⁺-doped Cs₃Tb/EuCl₆ enable a dual-mode color and spectral encoding strategy for optical anti-counterfeiting. This study highlights the versatile role of Sb³⁺ in tuning electronic structures and energy transfer, offering new insights for designing high-performance rare-earth halide materials for advanced optoelectronic applications.

Lead-free double perovskite (DP) materials have garnered growing interest because of their outstanding optoelectronic attributes. Nevertheless, realizing efficient, multimodal photoluminescence (PL) with adjustable emission spectra within single-host DP materials still poses a formidable hurdle. Herein, Er-based lead-free DPs (Cs₂NaErCl₆) were developed, which achieves downshift (DS) emissions from visible to near-infrared (NIR) and multicolor upconversion (UC) emissions, resulting from the abundant energy levels of Er³⁺ ions. Alloying with Yb³⁺ introduces new Yb³⁺-Er³⁺ cross-relaxation (CR) pathways, leading to a 308.5-fold increase in DS red emission and achieving a maximum color purity of 98.63%. Additionally, Yb³⁺ alloying enhances UC luminescence by 10.8-fold due to its strong absorption cross section around 980 nm. The colors of the UC emission can be adjusted by altering the doping concentration of Yb³⁺ and laser power density. Spectral analysis and theoretical calculations reveal the high compatibility of Yb³⁺ ions with Cs₂NaErCl₆, and the critical role of CR and energy-transfer processes in achieving efficient, tunable, and multimodal PL. Furthermore, the developed DP materials have been utilized in anticounterfeiting, information encoding, and narrow-band NIR photodetectors, expanding the versatile uses of rare-earth (RE)-based DP materials in the optoelectronics field.

The coordination structure of Sb³⁺ within the host lattice critically influences its photophysical properties, sparking interest in luminescent metal halides with multiexciton emissions. Furthermore, the multi‐coordination lattice structure of Sb³⁺ dynamically emits light with excitation wavelength, highlighting the potential of Sb³⁺ ions in tuning luminescence and developing advanced optoelectronic materials. Herein, Sb³⁺ ions are successfully doped into Cs₂SnCl₆, and the obvious excitation wavelength‐dependent emission of Cs₂SnCl₆: Sb at room temperature is observed. To explain this phenomenon, density functional theory (DFT) calculations and time‐resolved spectra are conducted to confirm that the emission originated from two luminescence centers associated with the [SbCl₆]³⁻ and [SbCl₅]²⁻ coordination. Based on the tunable emission of Cs₂SnCl₆: Sb and the effective electron transfer between two triplet self‐trapped exciton states induced by Bi³⁺ and Sb³⁺, a pixelated code for information encryption is designed. The encoded patterns exhibit color changes under different UV wavelengths, enabling secure and straightforward information encryption. Furthermore, a sensitive UV wavelength sensor is prepared based on Cs₂SnCl₆: Bi/Sb, exploiting the monotonic relationship between chromaticity coordinates and wavelength, achieving a resolution superior to previously reported wavelength sensors. This study marks a substantial step toward advancing the multifunctional application of lead‐free metal halides.

Fluorescence thermometry has garnered significant attention for its noninvasive, remote, highly sensitive, and rapid temperature measurement capabilities. However, achieving superior sensitivity at high temperatures remains a persistent challenge. Herein, a series of Rb _{2− x} Cs _x HfCl ₆ : y%Te ⁴⁺ perovskites are synthesized to investigate the impact exerted by A‐site regulating regarding the luminescence efficiency and temperature‐responsive capabilities. Te ⁴⁺ doping significantly enhances luminescence intensity, with the broadband yellow light resulting from electron–phonon coupling within the soft lattice, driven by self‐trapped exciton emission. Furthermore, A‐site regulation demonstrates that increasing Cs⁺ content induces enhanced Jahn–Teller distortion, thereby boosting luminescence efficiency. However, the pure Rb sample exhibits the lowest thermal activation energy, as the temperature rises, increased phonon‐exciton coupling and the defect activity accelerate the nonradiative recombination, drastically decreasing fluorescence lifetime by two orders of magnitude from 300 to 390 K. Utilizing this exceptional thermal sensitivity, a lifetime‐based fluorescence thermometer is developed, attaining a breakthrough relative sensitivity reaching 20.69% K ⁻¹ at 390 K, with high repeatability across multiple heating and cooling cycles. Additionally, a high‐temperature warning system for lubricating oil pipelines is designed, demonstrating robust monitoring capabilities. This work offers a new perspective on developing highly sensitive thermometers that utilize halide perovskites for high‐temperature applications.

For the first time, nanotubes of Y₃Ga₅O₁₂:Cr³⁺ (referred to as YGO:Cr³⁺) and Y₃Ga₅O₁₂:Cr³⁺/Yb³⁺ (referred to as YGO:Cr³⁺/Yb³⁺) were produced via a single-needle electrospinning method. The nanotubes of YGO:Cr³⁺ and YGO:Cr³⁺/Yb³⁺ have outer diameters between 190 and 210 nm, whereas the inner diameter ranges between 70 and 80 nm, and the wall thickness ranges from 50 to 60 nm. The temperature sensitivity of YGO:0.02Cr³⁺ nanotubes was examined by studying how the Cr³⁺ lifetime changes with temperature. In the temperature range of 303 to 723 K, the peak values of S_a and S_r were 0.274 and 0.0067 K^-1, respectively. Temperature sensing properties of YGO:0.02Cr³⁺/yYb³⁺ (y = 0.01, 0.02, and 0.05) nanotubes were evaluated via the FIR technique utilizing nonthermally coupled energy levels. The I₉₇₀/I₇₀₈ in the YGO:0.05Cr³⁺/0.01Yb³⁺ nanotubes displayed a maximal S_r value of 0.013 K^-1 at 633 K, which exceeds that of other Cr³⁺-doped NIR phosphors previously reported and is promising for high-temperature measurements.

Ns ² ions‐doped lead‐free perovskites have garnered significant attention for their potential in diverse optoelectronic applications, owing to their broad emission characteristics arising from self‐trapped excitons (STEs). Herein, high‐performance white light‐emitting diodes (WLEDs) for intelligent lighting are developed by Bi ³⁺ /Te ⁴⁺ co‐doped Cs ₂ SnCl ₆ . Effective energy transfer between the dual STE emissions results in tunable broadband emissions covering the full‐color region. Adjustable WLEDs containing cold‐ and warm‐white lighting are fabricated. The WLEDs have excellent luminescent performances coupled with adjustable correlated color temperatures of 6417 and 3829 K. This versatility allows them to meet lighting demand for different scenarios, which is essential for future WLEDs to achieve healthy lighting. In addition, the excellent white light emission characteristics can also be applied in the visible light communication (VLC) system, achieving a −3 dB bandwidth of 13.3 MHz and opening eye diagrams in the data rate range of 10–60 Mbps. This work represents a significant advancement toward building intelligent health lighting applications and achieving high‐quality light sources for VLC based on lead‐free perovskites.