Fuqian Yang

Cellulose, lignin, and coumarin—renewable biomass—span LEDs' hierarchy, from flexible substrates and light management to emitters and white-light systems for sustainable next-generation optoelectronics.

Current-assisted processing has increasingly been used to tune material microstructures and to heal structural flaws. At the heart of this technique is the interaction between electric current and the material, which induces localized heating, enhances atomic migration, and activates related physicochemical processes. In this work, we analyze the flow of electric current in an infinite conducting medium containing a planar crack, specifically a Griffith-like crack and a penny-shaped crack, and the resulting steady-state, current-induced temperature field. Closed-form solutions for both the electric field and the steady-state temperature field are obtained. The electric field exhibits a square-root singularity at the crack tip or edge; however, no corresponding singularity arises in the steady-state temperature field at the same location that could cause local melting and crack healing. It is the transient and singular behavior of Joule heat at the crack tip or edge that can generate local melting and initiate the healing process. To quantify this behavior, we introduce a local melting zone surrounding the crack tip or edge and derive an approximate expression for its size under the assumption that the relevant material constants, including the transfer rate of heat, are temperature-independent. The extent of this melting zone scales with both the input power and the duration of electric-current flow. Increasing the input power and the current-flow time likely enhances the effectiveness of current-assisted healing of structural flaws in metallic materials.

In this study, we analyze the electrical problem of an electrochemical cell composed of two parallel electrodes, where one electrode contains a disk-shaped conductive particle surrounded by a nonconductive material. Under the condition of quasi-steady state, the problem is formulated as a Fredholm integral Equation. Closed-form analytical solutions are derived for two limiting cases, while the general case is solved numerically. The analysis reveals that the normal component of the electric field, which is proportional to the current density, is nonuniformly distributed over the disk surface and exhibits a square-root singularity at the edge of the conductive disk. The strength of singularity increases as the spacing between the disk-like conductive particle and the counter electrode decreases. A similar singular behavior is expected in the ion flux at the particle edge due to the proportionality between the current density and the flux of electrolyte ions. This result suggests that nonuniform distribution of the normal current density on conductive particles in lithium-ion batteries is expected to develop even though they are in contact not only with the liquid electrolyte but also with surrounding nonconductive materials through multiple interfaces.

Micron-sized CsCl: Eu ²⁺ films synthesized using DI water at low temperatures, exhibiting strong blue photoluminescence peak at ∼442 nm with PLQY of ∼81% and FWHM of ∼29.4 nm.

Under an equal‐area constraint, this study uses a two‐dimensional, bidirectionally coupled diffusion–stress model to analyze lithium diffusion and stress evolution in regular geometries (circular and polygonal) and an irregular particle reconstructed from a scanning electron microscopy (SEM) image. The results reveal that higher circularity promotes more uniform distribution of lithium, reduces von‐Mises and shear stresses, and leads to smoother, more symmetric stress fields. Electrode particles of polygonal shapes experience the largest shear stress on surface, which can cause surface damage during lithiation. For electrode particles in the shape of equilateral triangle, the largest radial stress and circumferential do not appear at the electrode center. For electrode particles of irregular shape with high boundary curvature and geometric discontinuities, there are pronounced concentration hotspots and localized stress concentrations along the periphery. The shear stress associated with local sharp corners and depressions can cause cracking and fragmentation of irregular electrode particles. These findings demonstrate that particle morphology critically influences the spatiotemporal evolution of the physicochemical fields by altering diffusion pathways and introducing boundary constraints. Enhancing circularity and optimizing boundary smoothness can mitigate stress concentration and delay mechanical degradation, offering practical guidance for the rational design of electrode architectures.

The electrochemical performance of activated carbons (ACs) is highly dependent on the temperature, especially under extremely cold or hot conditions. A fundamental understanding of the temperature effects on the performance of ACs is essential for a variety of applications of AC-based supercapacitors (SCs). In this work, biowaste-derived ACs are used as electrode materials in symmetrical SCs with 1 M commercial electrolyte of SBP-BF₄ in PC. The electrochemical performance of the prepared ACs is systematically investigated in a temperature range of -20 °C to 60 °C. Key metrics of specific capacitance, energy and power densities, characteristic time, IR drop, and ionic diffusivity exhibit pronounced temperature dependence, highlighting strong temperature effects. Increasing the temperature leads to increases in the specific capacitance, the characteristic time, and the nominal diffusivity of electrolyte ions. The temperature dependence of the nominal diffusivity follows the Arrhenius relation with the two regimes, likely indicating a change in the behavior of ionic diffusion. The difference between the energy barrier for electrolyte-ion adsorption onto the AC surface and that for ion desorption from the AC surface increases with increasing current density.

Understanding contact-induced damage is of paramount importance in the analysis of the lifespan and performance of surface coatings. In this work, we investigate the effects of dopants and interlayers on the structural durability of diamond-like carbon coatings (DLCs) and molybdenum disulfide (MoS₂) coatings on stainless steel via micro-scratch tests. The analysis of XPS survey spectra and Raman spectra of DLCs shows that the ratio of sp²/sp³ (i.e., the intensity ratio of sp² over sp³ obtained by XPS) is proportional to I_D/I_G, where I_D and I_G are the intensities of D and G bands of the Raman spectra. The analysis of the scratch tests reveals that there are three critical loads for the scratch-induced damage of the DLCs and MoS₂ coatings, corresponding, respectively, to the initiation of periodic V-cracking, the minimum load for periodic semicircle cracking or peel-off, and the minimum load for partial and periodic delamination. Dopants can reduce the friction coefficient of the DLCs and have negligible effect on the Ti/MoS₂ coatings. The Cr interlayer can better enhance the bonding strength between the DLCs and the steel substrate than the Si interlayer. Doping Cr and H can reduce the hardness of DLCs; doping Si can increase the hardness of the DLCs; and doping Ti, Pb, and PbTi can reduce the hardness of the MoS₂ coatings. Deep Symbolic Optimization (DSO) algorithm is used to establish nominal-mathematical formulations between the critical variables for the scratch test and the materials parameters of the surface coating. The DSO analysis demonstrates the feasibility of using “deep-learning” to establish “quantitative” relationships between the critical variables for mechanical deformation and materials parameters.

Ultrasmall perovskite CsPbBr ₃ quantum dots (QDs) with blue emission are promising materials for light‐emitting diodes (LEDs). However, achieving room‐temperature synthesis of blue‐emitting CsPbBr ₃ QDs with long‐term stability remains a major challenge, hampering their real‐world applications. Herein, we report a novel room‐temperature strategy for synthesizing highly stable, blue‐emitting CsPbBr ₃ QDs, achieved with cross‐linked network structures—marking a significant advancement over conventional approaches. Polymer (dimethyl siloxane dimethyl vinyl terminated (PDMS)) cross‐linked by curing agent (dimethyl methyl hydrogen siloxane) offers networks that control the size of CsPbBr ₃ QDs around 5 nm. The networks inhibit the fall‐off of ligands from the QD surface, which restrains the agglomeration of QDs and mitigates thermal quenching of light emission. The CsPbBr ₃ QDs with a photoluminescence quantum yield (PLQY) of 93% remain monodispersed in solution over 30 days. The QD‐based films retain 95% of their initial PLQY after thermal treatment at 120°C. Blue‐emitting CsPbBr ₃ LEDs with an emission of 472 nm and a full‐width at half‐maximum (FWHM) of 23 nm exhibit a peak luminance of 4096 cd m ⁻² and an excellent operational half‐lifetime ( T ₅₀ ) over 38 h at 100 cd cm ⁻² , the longest‐lifespan perovskite blue‐quantum‐dot LEDs reported to date.

Strained semiconductor quantum wells have been an active area of research for more than three decades. However, a major part of the reported literature has shown a core focus on the theoretical and experimental investigations of their energy band structures under different internal and external perturbations, taking strain parameters as the basis and studying their resulting effects on various optoelectrical properties of the strained quantum wells. However, since stress parameters can be measured more easily and with an enhanced level of accuracy compared to strain parameters, developing a stress-based analytical framework offers distinct advantages. This study focuses on the theoretical formulation of the bandgap evolution under different stress perturbations, namely, uniaxial, biaxial, and torsional stresses. Among these, biaxial and torsion stress perturbations have been incorporated for the first time in a unique manner for analyzing the bandgap of stressed quantum wells. Further, various constraints including zone center conditions, 1D quantum well potential, and anisotropic cubic symmetry have been incorporated during the formulation of stressed semiconductor quantum wells to reduce the complexity of formulation and, hence, providing a baseline study for future research of multi-dimensional potentials and complex internal or external perturbations.