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Flexible Organic Solar Cells Over 15% Efficiency with Polyimide-Integrated Graphene Electrodes
摘要： A highly flexible and durable transparent graphene electrode with thermal stability was developed via the direct integration of polyimide (PI) on graphene. Due to the high transparency of PI-integrated graphene electrode and intimate contact between graphene and PI substrate, high-efficiency flexible organic solar cell with a PCE of 15.2% and outstanding mechanical robustness was obtained.
关键词： Thermal Stability,High Efficiency,Polyimide-Integrated Graphene Electrodes,Flexible Organic Solar Cells,Mechanical Robustness
更新于2025-09-23 15:21:01
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Thermal stability study of transition metal perovskite sulfides
摘要： Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials. Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, a-SrZrS3, b-SrZrS3, BaZrS3, Ba2ZrS4, and Ba3Zr2S7. These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden–Popper phases. Differential scanning calorimeter and thermogravimetric analysis measurements were performed up to 1200 °C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 550 °C.
关键词： differential scanning calorimeter,thermoelectric materials,Transition metal perovskite chalcogenides,thermal stability,thermogravimetric analysis,Raman spectroscopy,Ruddlesden–Popper phases,X-ray diffraction,energy dispersive analytical X-ray spectroscopy
更新于2025-09-23 15:21:01
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A novel star-shaped, cardanol-based bio-prepolymer: Synthesis, UV curing characteristics and properties of cured films
摘要： Starting from renewable Cardanol, a novel inherently fire-retardant UV curable bio-based prepolymer (AEHCPP) with phosphazene core and six Cardanol arms are prepared in this report. The chemical structure of all newly prepared intermediates compounds and AEHCPP are well-characterized using nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). UV-curable mixture consisting of AEHCPP and different diluents were formulated and their photopolymerization dynamics were investigated on Photo-calorimetry (photo-DSC). The thermal properties of crosslinked coatings were estimated using thermal analysis technology. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) results show that glass transition temperatures of all cured films are above room temperature (>30oC), the 5% weight loss temperature in nitrogen is higher than 266oC. The fire-retardant properties are estimated by TGA and all calculated Limiting Oxygen Index (LOI) values are over 24, implying the excellent fire-resistance of cured films.
关键词： inherent fire-retardancy,bio-based UV coating,thermal stability,star-shaped Bio-based prepolymer,Cardanol,phosphazene core
更新于2025-09-23 15:21:01
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Chemically resistant and thermally stable quantum dots prepared by shell encapsulation with cross-linkable block copolymer ligands
摘要： Endowing quantum dots (QDs) with robustness and durability have been one of the most important issues in this field, since the major limitations of QDs in practical applications are their thermal and oxidative instabilities. In this work, we propose a facile and effective passivation method to enhance the photochemical stability of QDs using polymeric double shell structures from thiol-terminated poly(methyl methacrylate-b-glycidyl methacrylate) (P(MMA-b-GMA)-SH) block copolymer ligands. To generate a densely cross-linked network, the cross-linking reaction of GMA epoxides in the PGMA block was conducted using a Lewis acid catalyst under an ambient environment to avoid affecting the photophysical properties of the pristine QDs. This provides QDs encapsulated with robust double layers consisting of highly transparent PMMA outer-shell and oxidation-protective cross-linked inner shell. Consequently, the resulting QDs exhibited exceptional tolerance to heat and oxidants when dispersed in organic solvents or QD-nanocomposite films, as demonstrated under various harsh conditions with respect to temperature and oxidant species. The present approach not only provides simple yet effective chemical means to enhance the thermochemical stability of QDs, but also offers a promising platform for the hybridization of QDs with polymeric materials for developing robust light-emitting or light-harvesting devices.
关键词： photochemical stability,block copolymer ligands,oxidative stability,cross-linking,thermal stability,quantum dots
更新于2025-09-23 15:19:57
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Effect of Sr substitution on the air-stability of perovskite solar cells
摘要： By using a two-step spin-coating method, 10 mol% SrI2 and 10 mol% SrCl2-substituted perovskite films were synthesized and utilized to construct mesoscopic perovskite solar cells (PSCs), respectively. The influences of Sr substitutions on the humidity and thermal stability of PSCs were systematically investigated. It is indicated that both 10 mol% SrI2 substitution and 10 mol% SrCl2 substitution can enhance the power conversion efficiency (PCE) of PSC to more than 15%. The 10 mol% SrCl2 substitution can improve the humidity resistance of perovskite films, which is conducive to inhibiting the increase of perovskite’s defect density caused by humidity. After storing at 20±5 (cid:1), 30±5%RH for 21 d, the 10 mol% SrCl2-substituted PSC can still maintain 84% of the initial efficiency. However, the 10 mol% SrI2-substituted PSC exhibits a strong humidity sensitivity, which results in the increase of series resistance and the decrease of recombination impedance, thus making the PCE decrease to less than 20% of the initial value after storing at 20±5 (cid:1), 30±5%RH for 21 d. As for the thermal stability of PSCs, both the 10 mol% SrI2 and 10 mol% SrCl2-substituted perovskite films exhibit a certain thermal resistance. After 18 thermal cycles, both the 10 mol% SrI2 and 10 mol% SrCl2-substituted PSCs can maintain over 90% of the initial PCEs.
关键词： Perovskite solar cells,Sr-substituted perovskites,Humidity stability,Thermal stability
更新于2025-09-23 15:19:57
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Improved Chemical Stability of Organometal Halide Perovskite Solar Cells against Moisture and Heat by Ag Doping
摘要： Organometal halide perovskite (OHP) solar cells have been intensively studied because of their promising optoelectronic features, which has resulted in a high power conversion efficiency > 23%. Although OHP solar cells exhibit high power conversion efficiencies, their relatively poor stability is a significant obstacle to their practical use. We report that the chemical stability of OHP solar cells with respect to both moisture and heat can be improved by adding a small amount of Ag to the precursor. Ag doping increases the size of the OHP grains and reduces the size of the amorphous intergranular regions at the grain boundaries, and thereby hinders the infiltration of moisture into the OHP films and their thermal degradation. Quantum mechanical simulation reveals that Ag doping increases the energies of both the hydration reaction and heat-induced vacancy formation in OHP crystals. This procedure also improves the power conversion efficiencies of the resulting solar cells.
关键词： Perovskite solar cells,doping,thermal stability,moisture stability,Crystal engineering
更新于2025-09-23 15:19:57
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Structural Evolutions of Vertically-Aligned Two-Dimensional MoS <sub/>2</sub> Layers Revealed by <i>In Situ</i> Heating Transmission Electron Microscopy
摘要： Benefited from a large density of layer edges exposed on the surface, vertically-aligned two-dimensional (2D) molybdenum disulfide (MoS2) layers have recently harvested excellent performances in the field of electrochemical catalysis and chemical sensing. With their increasing versatility for high-temperature demanding applications, it is vital to identify their thermally-driven structural and chemical stability as well as clarify its underlying principle. Despite various ex situ and in situ characterizations on horizontally-aligned 2D MoS2 layers, the direct in situ heating of vertically-aligned 2D MoS2 layers and the real-time observation of their near-atomic scale dynamics have never been approached, leaving their thermal stability poorly understood. Moreover, the geometrical advantage of the surface-exposed vertically-aligned 2D MoS2 layers is anticipated to unveil the structural dynamics of interlayer van der Waals (vdW) gaps and its correlation with thermal energy, unattainable with 2D MoS2 layers in any other geometry. Herein, we report a comprehensive in situ heating TEM study on cleanly transferred vertically-aligned 2D MoS2 layers up to 1000 °C. Several striking phenomena were newly observed in the course of heating: (1) formation and propagation of voids between the domains of vertical 2D MoS2 layers with distinct grain orientations starting at ~875 °C, (2) subsequent decompositions of the 2D MoS2 layers accompanying a formation of Mo nanoparticles at ~950 °C, much lower than the melting temperature of their bulk counterpart, and (3) initiation of decomposition from the surface-exposed 2D layer vertical edge sites, congruently supported by molecular dynamics (MD) simulation. These new findings will offer critical insights into better understanding the thermodynamic principle that governs the structural stability of general vdW 2D crystals as well as providing useful technological guidance for materials design and optimization in their potential high-temperature applications.
关键词： van der Waals gaps,in situ heating,structural evolution,MoS2,two-dimensional,vertically-aligned,transmission electron microscopy,thermal stability,molecular dynamics simulation
更新于2025-09-23 15:19:57
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All vacuum deposited and thermally stable perovskite solar cells with F4-TCNQ/CuPc hole transport layer
摘要： Hole transporting layers (HTLs) play a crucial role in realization of efficient and stable perovskite solar cells (PSCs). Copper Phthalocyanine (CuPc) is one of the promising HTLs owing to its thermal stability and favorable band alignment with perovskite absorber. However, the power conversion efficiency (PCE) of PSCs with CuPc HTL is still lag behind highly efficient solar cells. Herein, a p-type F4-TCNQ is employed as an interlayer between the perovskite and CuPc HTL in all vacuum deposited PSCs. The F4-TCNQ interlayer improves the conductivity of both MAPbI3 and CuPc, reduces the shunt pathway and facilitates an efficient photoexcited holes transfer from the valance band of the MAPbI3 to LUMO of the F4-TCNQ. Consequently, a best solar cell device with F4-TCNQ interlayer achieved the PCE of 13.03% with a remarkable improvement in fill factor. Moreover, the devices showed superior stability against thermal stress at 85 ?C over 250 hours and retained ~95% of its initial efficiency. This work demonstrates a significant step towards all vacuum deposited perovskite solar cells with high thermal stability.
关键词： Perovskite solar cells,interlayer,thermal stability,vacuum deposition
更新于2025-09-23 15:19:57
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Novel red emitting LnTaO4: Eu3+ (Ln = La, Y) phosphors for warm white LEDs
摘要： LnTaO4: Eu3t (Ln ? La, Y) phosphors were synthesized by high-temperature solid-state reaction. Powder X-ray diffraction analysis confirmed the pure phase formation. Diffuse reflection spectra, excitation and emission spectra, the CIE chromaticity coordinates as well as the temperature-dependent emission spectra were investigated those phosphors. Upon near UV and blue excitation LnTaO4: Eu3t (Ln ? La, Y) show intense red emission of Eu3t. The optimum concentration of Eu3t in LaTa1-xEuxO4 phosphor was x ? 0.20, and concentration quenching mechanism was the electric dipole-dipole interaction. Furthermore, the critical transfer distance was obtained and the CIE chromaticity coordinates of LaTaO4: Eu3t samples were close to the National Television System Committee standard values. The temperature-dependent luminescence indicated LaTaO4: Eu3t exhibited moderate thermal stability. Those results suggested that LnTaO4: Eu3t (Ln ? La, Y) as red emitting phosphors could be potential candidates for white LEDs.
关键词： Luminescent properties,Red emitting phosphors,White LED,Thermal stability
更新于2025-09-23 15:19:57
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Design of a Broadband NIR Phosphor for Security-Monitoring LEDs: Tunable Photoluminescence Properties and Enhanced Thermal Stability
摘要： Near-infrared (NIR) phosphors with capability for blue light to 850 nm broadband NIR emission conversion are highly desirable for security-monitoring LEDs. Targeted phosphor LaSc2.93-yGayB4O12(LSGB): 0.07Cr3+ (y = 0.6) is designed from the initial model of LaSc2.93B4O12(LSB): 0.07Cr3+ by chemical composition modification. The correlations among crystal-field environment, structural evolution, and luminescence properties of LSGB: 0.07Cr3+ (0 ≤ y ≤ 1.5) are elucidated by the Dq/B values, decay curves, and polyhedron distortion. The substitution of Sc3+ by Ga3+ in LSGB: Cr3+ (0 ≤ y ≤ 1.5) leads to decreasing structural polyhedron distortion and strengthened crystal field, consequently resulting in the blue-shift of broadband emission and enhanced thermal stability of LSGB: 0.07Cr3+ (y = 0.6) compared to that of LSB: 0.07Cr3+. The above results demonstrate that the superiority of blue-shift and enhanced thermal stability of LSGB: 0.07Cr3+ (y = 0.6) make it more suitable for the blue-pumped security-monitoring LEDs.
关键词： luminescence properties,crystal-field environment,security-monitoring LEDs,thermal stability,structural evolution,LaSc2.93-yGayB4O12(LSGB): 0.07Cr3+,Near-infrared (NIR) phosphors
更新于2025-09-23 15:19:57