Lei Zhong

Mechanoluminescence (ML) materials, capable of converting mechanical action into light emissions, hold great promise for stress‐sensing applications. However, the lack of general design principles for developing efficient and self‐powered ML materials has significantly impeded progress in this field. Herein, we report a novel class of self‐powered Sr ₃ P ₄ O ₁₃ (SPO) ML materials enabled by energy transfer from electron‐hole pair recombination induced by contact electrification. Through combined analyses using piezoresponse force microscopy (PFM), thermoluminescence (TL) spectroscopy, triboelectric potential measurements, temperature‐dependent ML spectra, and density functional theory (DFT) calculations of charge density difference, the underlying ML mechanism is elucidated as contact electrification‐induced energy transfer. Systematic investigation of SPO:Bi and a series of SPO:RE (RE = Eu, Tb, Dy, Sm, Er, Tm) phosphors reveals that activator ions possessing spin‐allowed broadband absorption are favorable for achieving efficient ML, a correlation that extends consistently to radioluminescence (RL) and cathodoluminescence (CL) behaviors. Leveraging the favorable luminescence performance, we demonstrate proof‐of‐concept applications in a single material platform that integrates handwritten signature authentication, structural health monitoring, X‐ray imaging, optical temperature sensing, and multi‐stimulus information encryption. This work provides fundamental insights into contact electrification‐induced ML and establishes important design guidelines for developing efficient ML materials and their versatile applications.

The advancement of near‐infrared phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) for next‐generation optoelectronic applications is critically dependent on the availability of high‐performance phosphors. In this study, a series of NIR‐emitting phosphors with high luminescence efficiency and excellent stability was developed by co‐doping Cr ³⁺ , Yb ³⁺ into the Mg ₂ SiO ₄ (MSO) host. Efficient energy transfer from Cr ³⁺ to Yb ³⁺ was achieved in the MSO: Cr ³⁺ , 2.5%Yb ³⁺ phosphor, reaching an energy transfer efficiency of 91.82%, as determined from the luminescence intensity measurement. The optimal MSO: Cr ³⁺ , 1.5%Yb ³⁺ phosphor exhibits a remarkable internal quantum efficiency (IQE) of 71.8% and an external quantum efficiency (EQE) of 48.8%. It also demonstrates remarkable thermal stability, retaining 71.5% of its initial intensity at 423 K. Additionally, the material shows exceptional humidity resistance, retaining approximately 98.05% of its initial intensity after 7 days of exposure to harsh conditions (85°C and 85% relative humidity, RH). Notably, no significant chromaticity shift is observed at elevated temperatures, indicating excellent color stability. Finally, an NIR pc‐LED was fabricated by combining the optimized phosphor with a 450 nm commercial blue LED chip. The device delivers a high output power of 718.67 mW with an electro‐optical conversion efficiency of 12.53% at a driving current of 600 mA. Collectively, these results underscore the promising potential of this phosphor for applications in optical bioimaging and night vision.

Broadband near-infrared (NIR) light sources that combine high power, high efficiency, and wide spectral coverage are essential for emerging applications in imaging, sensing, and illumination. Phosphor-converted light-emitting diodes (pc-LEDs) offer a scalable platform for such sources, but their performance is often limited by weak visible-light absorption of d -electron emitters originating from parity-forbidden transitions. Here we report a symmetry engineering strategy that overcomes this limitation by partially relaxing the parity selection rules in Cr ³⁺ -activated systems. Controlled lattice perturbations in a rigid silicate framework break the local symmetry of Cr ³⁺ -coordinating octahedra, significantly enhancing blue-light absorption without increasing dopant concentration. In parallel, crystallographically distinct sites enable efficient inter-site energy funneling, directing excitation toward energetically favourable emission centers and improving radiative efficiency. The optimized phosphor exhibits broadband NIR emission at λ _max ~ 880 nm with an internal and external quantum efficiency of 93% and 64%, among the highest reported values and along with excellent thermal and environmental stability. When integrated with a blue InGaN chip, the phosphor-converted device enables watt-level NIR output with excellent operational stability. These results highlight the role of local structural control in improving the performance of d-electron emitters and provide a viable route towards efficient broadband NIR light sources.

Multimodal luminescent materials displaying dynamically tunable multicolor emissions under diverse excitation channels are at the core of optical information encryption technologies. However, simultaneous achievement of high‐performance multimodal luminescence with anti‐thermal quenching (ATQ) feature remains a critical challenge. Herein, a new class of SrZnP ₂ O ₇ :RE (RE = Sm ³⁺ , Dy ³⁺ , Tb ³⁺ , Tm ³⁺ ) phosphors is developed to fulfill these requirements through precise defect engineering. These phosphors exhibit photoluminescence (PL), radioluminescence (RL), mechanoluminescence (ML), thermoluminescence (TL), and persistent luminescence (PersL) with emission spanning 350–750 nm. By strategically incorporating charge compensators (Li ⁺ , Na ⁺ , K ⁺ ), precise regulation of trap distribution and density is demonstrated, yielding remarkable enhancements in PL, quantum efficiency, RL intensity, and X‐ray afterglow duration. Crucially, the engineered deep traps in Sm/Dy/Tm‐doped systems enable exceptional ATQ behavior. Comprehensive investigations reveal the critical role of charge compensation and defect redistribution in modulating luminescence performance. Benefiting from their superior multimodal emission properties, these phosphors demonstrate great promise for X‐ray imaging and high‐security anti‐counterfeiting/encryption applications. This work establishes a new paradigm in luminescent material design, providing both fundamental insights into defect‐luminescence property relationships and a practical framework for constructing advanced optical materials with tailored multimodal responses through precision trap state engineering.

Near‐infrared (NIR) light sources hold great potential for applications in night vision illumination, bio‐imaging, and non‐destructive testing. However, radiationless de‐activation and low absorption restrict the development of high‐efficiency blue light excitable NIR phosphors, especially for emissions beyond 900 nm. Herein we report a high‐performance Cr ³⁺ ‐activated forsterite (Mg ₂ SiO ₄ :1.5%Cr ³⁺ , 5%Li ⁺ ) phosphor exhibiting broadband NIR emission peaking at 960 nm with a record external quantum efficiency (EQE) up to 48%. The introduction of Li ⁺ as a charge compensator and symmetry distorter not only suppresses Cr ⁴⁺ formation but also enhances the cross section of Cr ³⁺ d ‐ d forbidden transitions in Mg ₂ SiO ₄ . More importantly, Li ⁺ promotes excited‐state energy transfer between Cr ³⁺ emitters, yielding exceptional thermal stability and external quantum efficiency. A fabricated NIR phosphor‐converted light‐emitting diode (LED) achieved a NIR radiated power of 356 mW (at a driving current of 700 mA) and an electro‐optical conversion efficiency up to 12.9% (at 100 mA). This work unlocks new possibilities for smart spectroscopy applications, from non‐destructive testing to human angiography and biometric recognition.

Optical thermometry has emerged as a promising technology to overcome the limitations of traditional thermometry techniques. Herein, we report an Eu³⁺-activated tungstate Ba₂CaWO₆ phosphors for luminescent thermometry with a maximum relative sensitivity of 4.84% based on a single-band ratiometric technique. By monitoring the ⁵D₀ → ⁷F₁ (595 nm) emission of Eu³⁺, excitation spectrum of the as-prepared sample was measured, showing a dominant broad band ranging from 240 to 345 nm corresponding to the O²⁻-W⁶⁺ charge transfer band (CTB). The intensity of CTB gradually decreases and the CTB edge shows an appreciable red shift when the temperature increases due to thermal population of the [WO₆]⁶⁻ moiety at higher vibrational levels. The opposite temperature dependences of the two specific excitations, one at the peak of CTB and the other from the edge of CTB, were employed to design a luminescence intensity ratio thermometry scheme in the tungstate. When compared to other related schemes, our scheme showed a higher relative sensitivity.

A novel ultra-sensitive ratiometric luminescence thermometry strategy combining the redshift of the charge transfer band with dramatic quenching of the intervalent charge transition in MgNb ₂ O ₆ :Dy ³⁺ /Pr ³⁺ thermochromic phosphors.