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Novel highly luminescent double-perovskite Ca2GdSbO6:Eu3+ red phosphors with high color purity for white LEDs: Synthesis, crystal structure, and photoluminescence properties
摘要： High-efficiency red-emitting phosphors are required to fabricate high-performance white light-emitting diodes (LEDs). Herein, the novel highly efficient Eu3+-activated Ca2GdSbO6 double-perovskite red phosphors with good thermal stability toward warm-white LEDs were reported. A series of Ca2Gd(1-x)EuxSbO6 red phosphors with different Eu3+ doping concentrations (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by using high-temperature solid-state reaction method. Under the excitation of 396 nm near-ultraviolet light, these Ca2Gd(1-x)EuxSbO6 phosphors showed intense red emissions peaking at 612 nm due to the 5D0→7F2 transition of Eu3+ ions. The strongest luminescence intensity reached when Eu3+ doping concentration was x = 0.5, and the critical distance between Eu3+ activators was calculated to be 7.97 ?. The concentration quenching mechanism was due to the dipole-dipole interaction of Eu3+ ions. The CIE color coordinates of the optimal Ca2Gd0.5Eu0.5SbO6 phosphors were determined to be (0.6629, 0.3367), and the corresponding color purity reached about 94.9%. Importantly, the Ca2Gd0.5Eu0.5SbO6 phosphors revealed outstanding internal quantum efficiency of 73% and good thermal stability. The emission intensity of Ca2Gd0.5Eu0.5SbO6 phosphors at 423 K still remained about 73% of its initial value at 303 K. Finally, a prototype white LED device was fabricated by coating the phosphor blend of commercial blue-emitting BaMgAl10O17:Eu2+ and our as-prepared red-emitting Ca2Gd0.5Eu0.5SbO6 on a 395 nm LED chip. Under 20 mA driven current, the device showed bright warm-white light with CIE color coordinates of (0.3888, 0.3943), correlated color temperature of 3911 K, and color rendering index of 88.4. The results demonstrated that the developed novel red-emitting Ca2Gd0.5Eu0.5SbO6 phosphors could be used as potential color converters in white LEDs.
关键词： White LEDs,Photoluminescence,Ca2GdSbO6,Double-perovskite,Eu3+ ions,Red-emitting phosphors
更新于2025-09-23 15:19:57
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Vapora??Deposited Cs <sub/>2</sub> AgBiCl <sub/>6</sub> Double Perovskite Films toward Highly Selective and Stable Ultraviolet Photodetector
摘要： Double perovskites have shown great potentials in addressing the toxicity and instability issues of lead halide perovskites toward practical applications. However, fabrication of high-quality double perovskite thin films has remained challenging. Here, sequential vapor deposition is used to fabricate high-quality Cs2AgBiCl6 perovskite films with balanced stoichiometry, superior morphology, and highly oriented crystallinity, with an indirect bandgap of 2.41 eV. Using a diode structure, self-powered Cs2AgBiCl6 ultraviolet (UV) photodetectors are demonstrated with high selectivity centered at 370 nm, with low dark current density (≈10?7 mA cm?2), high photoresponsivity (≈10 mA W?1), and detectivity (≈1012 Jones). Its detectivity is among the highest in all double-perovskite-based photodetectors reported to date and surpassing the performance of other perovskite photodetectors as well as metal oxide in the UV range. The devices also show excellent environmental and irradiation stability comparable to state-of-the-art UV detectors. The findings help pave the way toward application of double perovskites in optoelectronic devices.
关键词： double perovskite films,sequential vapor deposition,selective detection,ultraviolet photodetectors
更新于2025-09-23 15:19:57
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Ultraviolet-Protective Transparent Photovoltaics Based on Lead-free Double Perovskites
摘要： Perovskite solar cells have attracted great research interest as a promising candidate to silicon solar cells. Plenty of work has been reported to employ perovskites to semitransparent windows and transparent photovoltaic (TPV) devices to obtain multi-functional systems. However, the narrow bandgap and sharp absorption edge of the typical perovskites prevent them from achieving the highest transparency to satisfy the requirements of aesthetic and integration, and the poor stability and toxic Pb compositions hinder their practical application. Herein, we introduce lead-free halide double perovskites with wide bandgap and indirect bandgap character to fabricate long-term stable transparent photovoltaic devices exhibiting high visible transmittance (73%) and considerable energy conversion efficiency (1.56%). Through further theoretical calculation and evaluation, a new strategy by employing indirect bandgap material on TPV devices was proposed to combine the enhancement of these two parameters. This approach will be a significant compliment to near-infrared absorbing solar cells to selectively harvest light in the invisible region to obtain highly performing multi-junction smart windows on buildings, vehicles and mobile electronics, providing new reasonable idea to realize TPVs with high efficiency and transparency simultaneously.
关键词： double perovskite,transparent photovoltaic,optimization,indirect bandgap
更新于2025-09-23 15:19:57
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Synthesis and photoluminescence properties of a new blue-light-excitable red phosphor Ca2LaTaO6:Eu3+ for white LEDs
摘要： In this paper, a series of Eu3+-activated double-perovskite Ca2LaTaO6 (abbreviated as CLT:xEu3+; x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) red-emitting phosphors have been successfully synthesized via the conventional high-temperature solid-state reaction method. These samples were characterized by X-ray diffraction, Rietveld refinement, field-emission scanning electron microscope, elemental mapping, energy-dispersive spectrum, room-temperature photoluminescence, decay lifetimes, quantum efficiency, CIE color coordinates, and temperature-dependent emission spectra. Interestingly, under blue excitation into the 7F0→5D2 transition of Eu3+ at 466 nm, the CLT:xEu3+ phosphors could emit bright red light corresponding to the 5D0→7FJ (J = 1, 2, 3, 4) transitions. Their luminescence properties have been investigated as a function of the Eu3+ ions concentration. It was found that the CLT:0.4Eu3+ sample exhibited the strongest emission intensity, and the concentration quenching effect was caused by the dipole-dipole interaction among Eu3+ activators. Impressively, the emission intensity of the as-prepared CLT:0.4Eu3+ phosphors was about 4.3 times higher than the commercial Y2O3:Eu3+ red phosphors. Moreover, the CLT:0.4Eu3+ sample had excellent CIE color coordinates of (0.665, 0.334) and supereminent color purity of 95.3%. Notably, the study on temperature-dependent emission spectra of the CLT:0.4Eu3+ sample revealed its good thermal stability and color stability at high temperatures. These excellent photoluminescence properties of CLT:0.4Eu3+ phosphors indicated their promising application potential in white light-emitting diodes as blue-light-excitable red phosphors.
关键词： Ca2LaTaO6,White LEDs,Red-emitting phosphors,Eu3+ ions,Double-perovskite,Photoluminescence
更新于2025-09-23 15:19:57
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(Ba,Sr)LaZnTaO6:Mn4+ far red emission phosphors for plant growth LEDs: structure and photoluminescence properties
摘要： It is necessary to develop novel high-efficient red or far-red-emitting in order to facilitate the phosphor-converted light-emitting diodes (pc-LEDs) for plant growth. This work reports a series of novel far-red emitting (Ba,Sr)LaZnTaO6:xMn4+ phosphors with double perovskite structure synthesized by traditional high-temperature solid-state reaction (SSR) process. The crystal structure and morphology of (Ba,Sr)LaZnTaO6 are investigated by high-resolution TEM, SEM, and XRD Rietveld refinement. The photoluminescece properties are systematically explored and analyzed by diffuse reflection (DR) spectra, photoluminescence emission (PL) and excitation (PLE) spectra, decay curves and temperature-dependent spectra. Mn4+ ions occupy Ta5+ sites located at [TaO6] octahedral emitting red light with peak at 698 nm in BaLaZnTaO6:Mn4+ and 695 nm in SrLaZnTaO6:Mn4+ under n-UV and blue light excitation. The critical quenching concentration of Mn4+ was determined to be 0.008. The concentration quenching mechanism could be a dipole-dipole interaction between Mn4+ ions. In addtion, the PL intensity of (Ba,Sr)LaZnTaO6:xMn4+ phosphors decrease with increasing temperature. The SrLaZnTaO6:xMn4+ sample has better thermal stability than BaLaZnTaO6:xMn4+. Interestingly, (Ba,Sr)LaZnTaO6:0.008Mn4+ exhibits outstanding internal quantum efficiency (IQE ≥ 80 %). Fianally, the fabricated of LEDs are combined with SrLaZnTaO6:0.008Mn4+ phosphors combined with 460 nm InGaN chips, which emit blue and red light. Based on above properties, the rare-earth-free (Ba,Sr)LaZnTaO6:xMn4+ phosphors have great potentials to be serviced as far-red emitting phosphors in high-power plant growth LEDS.
关键词： double perovskite structure,phosphor-converted light-emitting diodes,internal quantum efficiency,far-red emitting,plant growth,Mn4+,thermal stability,photoluminescence,solid-state reaction
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Eu3+ doped (Li, Na, K) LaMgWO6 red emission phosphors: An example to rational design with theoretical and experimental investigation
摘要： Various theoretical methods were comprehensively applied in (Li, Na, K) LaMgWO6: Eu3+ phosphors to achieve the rational design of phosphors. The detailed structural characteristics were analyzed by using geometric optimization and Rietveld analysis for the first time. The plane-wave density functional theory (DFT) was used for all electronic structure, electronic distribution, and phonon dispersion calculations. The evolution of the octahedral tilting in the (Li, Na, K) LaMgWO6 crystal structures was studied in detail. The relationship between crystal structure, environmental factors, Judd-Ofelt intensity parameters and fluorescence properties were analyzed. Combined with experimental results and theoretical calculations, the detailed luminescence process is deduced starting from the different ionic radius of Li+, Na+, and K+. Notably, the redshift of CTB can be ascribed to the value variation of environmental factors, which can represent the ionic radius, coordination number, covalency, and polyhedral tilting to qualify comparison and even quantify analysis.
关键词： Red emission,Phosphor,Double perovskite tungstate,Luminescence,CASTEP,Environmental factor
更新于2025-09-19 17:15:36
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Novel efficient deep-red-emitting Ca2LuTaO6:Mn4+ double-perovskite phosphors for plant growth LEDs
摘要： Deep-red-emitting phosphors are important for fabricating light-emitting diodes (LEDs) toward applications in plant growth lighting. Herein, we reported on novel efficient deep-red-emitting Mn4+-activated Ca2LuTaO6 (CLT) double-perovskite phosphors. A series of CLT:xMn4+ (x = 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) samples were prepared by the conventional high-temperature solid-state reaction technique, and they were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), elemental mapping, photoluminescence excitation and emission, decay curves, CIE chromaticity coordinates, internal quantum efficiency (IQE), and temperature-dependent emission spectra. The CLT host crystallized in a monoclinic structure with space group of P21/n, and it contained an octahedral site of TaO6 for Mn4+ doping. Impressively, under 351 ultraviolet light excitation these CLT:xMn4+ phosphors exhibited bright deep-red emissions around 682 nm with CIE chromaticity coordinates of (0.7272, 0.2728) and full width at half maximum (FWHM) of 25 nm. Notably, the optimal CLT:0.2%Mn4+ sample possessed an IQE of 37% and good resistance to thermal quenching (I423 K/I303K = 47%). Considering the emission spectrum of CLT:0.2%Mn4+ deep-red-emitting phosphors matched well with the absorption spectrum of phytochrome PFR, the as-prepared CLT:0.2%Mn4+ phosphors showed great potential in plant growth LEDs.
关键词： Deep-red emissions,Phosphors,Luminescence,Double-perovskite,Mn4+,Plant growth lighting
更新于2025-09-19 17:13:59
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Double perovskite Cs4CuSb2Cl12 microcrystalline device for cost effective photodetector applications
摘要： Recently reported double perovskites (DPs), Cs4CuSb2Cl12 has led to the development of a new lead free perovskite. It is 1 eV band gap material. The perovskite microcrystals were synthesized via liquid phase method. This was investigated as active solar energy materials for visible-light photodetector. The microcrystalline device was made in a single-step printable Cs4CuSb2Cl12/carbon materials composite paste. 10 wt % active material composite was found to be the best candidate for the highest responsivity, 10 ―3 A/W and detectivity, 108 J. One-step printing of the composite paste can be used for cost effective photodetector applications.
关键词： Photodetector,Solar energy materials,Cesium Copper Antimony Chloride (Cs4CuSb2Cl12),Carbon materials,Double Perovskite
更新于2025-09-12 10:27:22