Search

Developing violet‐light‐excitable deep‐red (650–660 nm) Eu2+‐activated phosphor is essential for full‐spectrum lighting. However, the related phosphors with facile synthesis, excellent optical performance, and superior thermal stability are scarce. Herein, a new class of (Sr,Ba)Lu2O4: Eu2+ deep‐red phosphor (660 nm) excitable by violet light via Ba2+‐induced local structure engineering is reported. Impressively, tunable emission from 615 to 682 nm, accompanied by significant improvement of thermal stability (81%@423 K), is achieved by partially substituting Sr2+ by Ba2+ in SrLu2O4: Eu2+. Crystal field analysis, density functional theory calculations, and thermoluminescence spectra confirm that the strong distortion and enhanced covalency of [EuO6] octahedron are responsible for spectral tunability, and the formation of shallow trapping states is beneficial for electron compensation to inhibit thermal quenching in the Sr0.85Ba0.15Lu2O4: Eu2+ phosphor. Finally, a white light‐emitting diode prototype fabricated by coupling of the Sr0.85Ba0.15Lu2O4: Eu2+ deep‐red phosphor and commercial blue/green phosphors with violet chip can yield sunlight‐like white light with an ultra‐high color rendering index (Ra = 95.2, R9 = 97.0) and an appropriate correlated color temperature of 4121 K, verifying its significant application potential in full‐spectrum solid‐state lighting. [ABSTRACT FROM AUTHOR]

Lead halide perovskite quantum dots (PeQDs) generally show slow hot carrier (HC) cooling because of the retarded relaxation of longitudinal optical (LO) phonons induced by hot phonon bottleneck effect. Although the feature is beneficial for designing photovoltaic devices beyond Schottky–Queisser limitation by manipulating HC excess energy, it would be hostile toward light‐emitting applications where fast HC cooling is preferred. Herein, a Ni2+ doping strategy is reported to effectively boost HC cooling in CsPbI3 PeQDs and inhibit Auger recombination, giving rise to near unity photoluminescent quantum yield (PLQY) for the Ni: CsPbI3 sample. Femtosecond transient (fs‐TA) absorption, temperature‐dependent PL spectra and theoretical calculations evidence that Ni2+ doping results in the enhancement of electron‐LO phonon coupling, the introduction of extra energy states at band edges, the increasement of effective carrier mass, and the modification of phonon dispersion spectra as well as density of states (DOS) of LO phonon modes. These synergistic roles ensure efficient Klemens decay within Ni: CsPbI3, which facilitates fast decay of hot phonons and break hot phonon bottleneck. These findings provide a valid route to tackle HC dynamics and pave a way for PeQDs‐based efficient light‐emitting applications. [ABSTRACT FROM AUTHOR]

Perovskite quantum dots (PeQDs) are seen as the credible alternative to traditional QDs ascolor converter in liquid crystal display (LCD). Unfortunately, PeQDs sufferfrom instability and color separation, and the prepared PeQDs enhanced films(PQDFs) need the protection of expensive barrier layers, which significantly increases price and limits their application. Herein, large‐area yellow monolithic PQDF is fabricated with both green CsPbBr3 and red CsPbBr1I2QDs encapsulated in the dual matrices of inorganic glass and polypropylene (PP) via an industrialized melt extruding & rolling method. The PQDF shows high photoluminescence quantum yield (PLQY) of 92% and narrow full width at half maximum (FWHM) of 19 nm (green) and 33 nm (red). Importantly, the bare PQDF without barrier layers can pass harsh aging test at 85 °C/85% RH and reach anoperating T90 lifetime over 1000 h. Finally, a white backlit unit is designed by coupling yellow monolithic PQDF with blue light guide panel, and the constructed prototype display shows superior color rendering performance forits narrow green/red emissions, reaching a color gamut of 110% National Television System Committee (NTSC). This work provides a novel and easy‐to‐industrialize route to prepare PQDFs to realize their commercial application in backlit display. [ABSTRACT FROM AUTHOR]

Due to their excellent optical performance, lead halide perovskite nanocrystals (PeNCs) have been widely used in optoelectronic devices. However, the presence of surface defects such as localized trap states severely hampers their practical application in optoelectronic fields. In this work, we have developed a simple method to reduce surface defects by introducing sulfuric acid after the nucleation of CsPbI3 PeNCs is complete. Sulfate ions effectively interact with the exposed metal lead ions on the surface of perovskite NCs, leading to surface passivation. This process represses nonradiative recombination and significantly enhances the luminescence efficiency of PeNCs. Moreover, the passivated CsPbI3 PeNCs with SO42– exhibit a lower overall energy-level structure compared to that of pristine CsPbI3 PeNCs, promoting improved electron injection. Benefiting from this highly effective passivation strategy, light-emitting diodes (LEDs) based on SO42–-passivated PeNCs exhibit an optimal external quantum yield of 9.94% and luminance of 2182 cd m–2, surpassing the performance of LEDs made from pristine PeNCs. [ABSTRACT FROM AUTHOR]

Laser‐driven projection display puts forward urgent demand for color converter materials to simultaneously achieve balanced‐spectrum properties and strong heat dissipation. Herein, this work develops a novel optofunctional composite by coupling Y3Al5O12:Ce3+ transparent ceramics (TC) with CaAlSiN3:Eu2+ phosphor‐in‐glass film (PiGF) for the first time. Remarkably, this new material architecture design enables a balance between the spectrum properties and heat dissipation ability, and can yield high‐quality white light with brightness of over 2500 lm, luminous efficacy (LE) of over 200 lm W−1, correlated color temperature (CCT) of 3700–4100 K, and improved color rendering index (CRI) of 60–70. Furthermore, the PiGF@TC‐converted laser projection system is also successfully designed, showing natural and real color restoration. Additionally, the combined action of thermal quenching and optical excitation intensity quenching is confirmed for the luminescence saturation upon high‐power blue laser driven. The main mechanism of optical quenching is identified to be energy upconversion dominated by second‐order nonlinear processes. The findings described here suggest a step toward developing the admirable laser‐driven color converters for next‐generation lighting sources. [ABSTRACT FROM AUTHOR]

Robust amorphous glass protected CsPbBr3 (CsPbBr3@glass) perovskite quantum dots (PeQDs) with ultra‐pure green emission and superior long‐term stability are highly desirable for developing wide‐color‐gamut liquid crystal displays. However, most of the reported CsPbBr3@glass nanocomposites are subject to low external quantum efficiency (EQE). This work demonstrates that ZrO2 additive has an "accumulation" effect on the borosilicate glass network structure to promote in situ nucleation/growth of PeQDs inside glass rather than self‐crystallization. This effect is beneficial in reducing surface defects, improving the quality of PeQDs, and thus boosting radiative recombination of excitons. As a consequence, the as‐prepared CsPbBr3@glass shows a record EQE of up to 75% and can pass the accelerated aging tests at 85 °C/85% RH for 1000 h and blue light irradiation over 2000 h. Finally, a prototype display using CsPbBr3@glass‐based straight‐down backlit unit is designed and gains more favorable responses in blind selection tests for its high brightness of 2647 cd m−2 and high color purity of 88%. The findings will pave the way for realizing the commercial application of CsPbBr3@glass nanocomposite in PeQDs‐converted backlit display. [ABSTRACT FROM AUTHOR]

Currently, lanthanide (Ln3+) doped Pb‐free double perovskites (DPs) suffer from competitive emissions of the self‐trapped exciton (STE) and Ln3+. Herein, a new type of Nd3+‐doped Cs2AgInCl6 DPs with Na+/Bi3+ co‐alloying is developed. Benefiting from Na+/Bi3+‐induced local structural modification, both STE broadband visible luminescence and Nd3+ near‐infrared (NIR) emissions are boosted via free exciton sensitization. Specifically, a total 648‐fold enhancement in emitting intensities compared to the Na+/Bi3+‐free counterpart is realized, with a significantly improved NIR photoluminescence quantum yield (PLQY) from 0.16% to 30.3%. First‐principles density functional theory calculations, Raman spectra, and steady/transient‐state PL spectra verify the modification of local site symmetry, breakdown of parity‐forbidden absorption, and reduction of electron‐phonon coupling via Na+/Bi3+ doping. Finally, a compact vis–NIR broadband light‐emitting diode (LED) is designed by coupling the Na/Bi/Nd: Cs2AgInCl6 DP with a commercial ultraviolet LED chip, which shows promising applications in spectroscopic analyses and multifunctional lighting. [ABSTRACT FROM AUTHOR]

Laser‐driven projector puts forward urgent demand for light‐conversion materials to achieve high‐quality image display. Herein, a composite structure phosphor‐in‐glass film (PiGF) is fabricated via screen‐printing YAG:Ce and low‐melting glass on the alumina substrate. Benefited from well‐retained optical properties of YAG:Ce in amorphous glass and high thermal conductivity of substrate, PiGF can produce desirable luminous flux of 7169 lm and luminous efficiency of 192 lm W−1 at saturation threshold of 13.25 W mm−2. Furthermore, it is demonstrated that thermal management by using a cool fan with aluminum heat sink is essential to reduce heat aggregation and improve white‐light stability of PiGF‐based laser lighting source operated in a reflective mode. Accordingly, a PiGF‐converted laser projection system is successfully designed for the first time, showing more vivid and brighter display feature benefited from high laser‐driven luminance of LCD screen (2180 cd m−2). This work highlights the practical application of PiGF@alumina‐substrate composite as an efficient laser‐driven color converter in high‐brightness projection display. [ABSTRACT FROM AUTHOR]

High‐quality backlit display puts forward urgent demand for color‐converting materials. Recently, metal halide perovskites (MHPs) with full spectral tunability, high photoluminescence quantum yields (PLQYs), and high color purity have found potential application in wide‐color‐gamut display. Regrettably, naked MHPs suffer from long‐term instable issue and cannot pass harsh stability tests. Herein, amorphous‐glass‐protected green/red CsPbX3 quantum dots (QDs) are prepared by elaborately optimizing glass structure, perovskite concentration, and in situ crystallization. PLQYs of green CsPbBr3@glass and red CsPbBr1.5I1.5@glass reach 94% and 78%, respectively, which are the highest ones of CsPbX3@glass composites reported so far and comparable to colloidal counterparts. Benefited from complete isolation of QDs from external environment by glass network, CsPbX3@glass can endure harsh commercial standard aging tests of 85 °C/85%RH and blue‐light‐irradiation, which are applied to construct white light‐emitting diodes (wLEDs) with high external quantum efficiency of 13.8% and ultra‐high luminance of 500 000 cd m−2. Accordingly, the perovskite wLED arrays‐based backlit unit and a prototype display device are designed for the first time, showing more vivid and wide‐color‐gamut feature benefited from narrowband emissions of CsPbX3 QDs. This work highlights practical application of CsPbX3@glass composite as an efficient and stable light color converter in backlit display. [ABSTRACT FROM AUTHOR]

Laser‐driven projection display puts forward urgent demand for color converter materials to achieve wide‐color‐gamut and high‐quality image presentation. In this study, a hierarchical structure quantum dots‐in‐glass film (QiGF) is fabricated via co‐sintering stable green/red‐emitting CsPbX3@glass (X3 = Br3, Br1.5I1.5) and commercial low‐melting glass on the sapphire substrate. Benefiting from the well‐retained optical properties of CsPbX3 quantum dots in amorphous glass and high thermal conductivity, QiGF succeeded in inhibiting luminescence saturation after 20 W mm−2 blue laser irradiation. A brand‐new white‐lighting source designed by coupling a blue laser with a pattern "QiGF wheel" produced ultra‐narrow blue/green/red tri‐color emissions and total luminous flux of 146 lm. Accordingly, a QiGF‐converted laser projection system is successfully designed for the first time, showing more natural and real color restoration for its wide color gamut display feature (157% of conventional light‐emitting diode projection and 107% of NTSC standard). The present study highlights the practical application of CsPbX3 quantum dots composite as an efficient laser‐driven color converter in projection display. [ABSTRACT FROM AUTHOR]

Cadmium sulfide has attracted wide attention in photocatalytic hydrogen production, due to its appropriate bandgap and band positions. However, high‐rate photogenerated electron–hole recombination and few active sites on CdS lead to its low photocatalytic activity. Herein, a PANI/NCPP/CdS (PANI/NiCoP/NiCoPi/CdS) hybrid as a noble metal‐free visible light‐driven photocatalyst is reported, with metal phosphides, metal phosphates, and polyaniline (PANI) as reduction and oxidation cocatalysts, respectively. This hybrid not only facilitates the charge separation and transfer owing to the formation of heterojunction, but also improves the local concentration of H+ on the surface of catalysts due to the formation of the protonated amine groups on PANI, beneficial to hydrogen evolution reaction. As a result, the as‐prepared photocatalyst could show a high hydrogen evolution rate of 170.3 mmol g−1 h−1 and an apparent quantum efficiency of 41.37% at 420 nm, representing one of the best performances of all‐CdS‐based photocatalysts. [ABSTRACT FROM AUTHOR]

Labels based on physical unclonable functions (PUFs) have been proven to be some of the most effective anticounterfeiting strategies. However, it is still challenging to develop PUF-based anticounterfeiting labels with low prices, simple manufacturing, and easy authentication. Herein, photochromic PUF labels are fabricated by randomly dispersing highly crystalline carbon nitride (HCCN) particles in poly-(vinyl acetate) (PVAc). The color of the PVAc/HCCN films originating from photochromism is used as the first layer of safety, which is verified by the naked eye. The pattern of the randomly distributed HCCN particles within the photochromic area (i.e., the PUF) is used as the second layer of security. The PUF can be read out by any smartphone equipped with a portable objective and then automatically authenticated by computer vision technology. We further prove the accurate and feasible authentication of the prepared PUFs and their application potentials. [ABSTRACT FROM AUTHOR]

Control of spins by spin–orbit torque brings novel strategies to design spintronic devices with potentially high impact in data storage and logic‐in‐memory computing architectures. Although various attempts have been proposed to avoid the participation of magnetic field during magnetization switching for realizing multifunctional spin logic devices, simpler and more feasible approaches are still strongly desired. Here, field‐free current‐induced magnetization switching is achieved through magnetic domain wall (DW) motion in a dual‐channels device, where the chiral Néel DW is stabilized by the strong Dzyaloshinskii–Moriya interaction in Pt/Co/Ru asymmetric structure. By electrically programming the initial magnetization states of the device with two opposite switching modes, four Boolean logic gates of AND, NAND, OR, and NOR are demonstrated. This work demonstrates that ingenious geometry design can be important for developing the spin logic devices and in‐memory computing architectures. [ABSTRACT FROM AUTHOR]

Exploiting the spin degree of freedom to store and manipulate information provides a paradigm for future microelectronics. The development of van der Waals (vdW) heterostructures has created a fascinating platform for exploring spintronic properties in the two-dimensional (2D) limit. Transition-metal dichalcogenides such as tungsten diselenide (WSe2) have electronic band structures that are ideal for hosting many exotic spin–orbit phenomena. Here, we report the spin-filtering effect in all-vdW heterostructures with WSe2 barrier. Combining 2D-perpendicular magnetic anisotropy Fe3GeTe2 (FGT) with different thicknesses of WSe2, the FGT/WSe2/FGT spin valve shows distinct charge and spin transport behavior. Moreover, the negative magnetoresistance (−4.3%) could be inverted into positive magnetoresistance (up to +25.8%) with decreasing the WSe2 thickness. Furthermore, we proposed a spin-filtering model based on Δ-symmetry electrons tunneling to explain the crossover from negative to positive MR signal through ab initio calculation. These experimental and theoretical results illustrate the rich potential of the families of TMDC materials to control spin currents in 2D spintronic devices. [ABSTRACT FROM AUTHOR]

Spintronics research has been of emerging interest in the inorganic and organic electronics field, and magnetic materials play an important role in spintronics. Here, the spin valve (SV) devices are reported based on few‐layered van der Waals semiconducting WSe2 or InSe sandwiched between room‐temperature ferromagnet Pt/Co/Ru and exfoliated layered ferromagnetic metal Fe3GeTe2 (FGT). The metallic interface rather than the Schottky barrier is formed despite the semiconducting nature of WSe2 and InSe, which may be originated from the interface hybridization with Pt/Co/Ru and FGT. The magnetoresistance of both devices persists up to the Curie temperature of FGT, and the magnitude of the magnetoresistance does not vary with the applied current, which indicates these devices have stable device performance. The work reveals that easily fabricated Pt/Co/Ru multilayers could be stable 3D perpendicular magnetocrystalline anisotropy (PMA) spin injection electrodes applied in SV devices, facilitated by combining 2D magnets, which is expected to be an attractive candidate for 2D applications. [ABSTRACT FROM AUTHOR]

Currently, advanced optical security techniques are imminent in response to the increasingly rampant counterfeit and pirated goods on a global scale. Herein, hexagonal Na(NdxY1−x)F4 (x = 0–1) solid‐solution nanocrystals (NCs) embedded glasses are successfully fabricated via in situ glass crystallization. Benefited from the protection of inorganic glass, Na(NdxY1−x)F4 NCs exhibit superior long‐term stability and can endure high‐power 808 nm laser irradiation. Importantly, opposite variations between near‐infrared (NIR) luminescence and laser‐induced temperature can be detected for the nanocomposites, which are sensitive to Nd3+ doping concentration. As a proof‐of‐concept experiment, Nd3+ concentration dependent anti‐counterfeiting patterns with high‐concealment and high‐precision are designed and show bright emission and dimmish thermal images in Nd3+‐tenuous composites under the irradiation of 808 nm laser, while opposite displays can be achieved in Nd3+‐enriched one. This kind of information encryption triggered by a commercial single light source to achieve dual opposing displays in one material can effectively improve security in anti‐counterfeiting. [ABSTRACT FROM AUTHOR]