Perovskite solar cells have recently drawn significant attention for photovoltaic applications with a certified power conversion efficiency of more than 22%. Unfortunately, the toxicity of the ...dissolvable lead content in these materials presents a critical concern for future commercial development. This review outlines some criteria for the possible replacement of lead by less toxic elements, and highlights current research progress in the application of low-lead halide perovskites as optically active materials in solar cells. These criteria are discussed with the aim of developing a better understanding of the physio-chemical properties of perovskites and of realizing similar photovoltaic performance in perovskite materials either with or without lead. Some open questions and future development prospects are outlined for further advancing perovskite solar cells toward both low toxicity and high efficiency.
Although low-temperature, solution-processed zinc oxide (ZnO) has been widely adopted as the electron collection layer (ECL) in perovskite solar cells (PSCs) because of its simple synthesis and ...excellent electrical properties such as high charge mobility, the thermal stability of the perovskite films deposited atop ZnO layer remains as a major issue. Herein, we addressed this problem by employing aluminum-doped zinc oxide (AZO) as the ECL and obtained extraordinarily thermally stable perovskite layers. The improvement of the thermal stability was ascribed to diminish of the Lewis acid–base chemical reaction between perovskite and ECL. Notably, the outstanding transmittance and conductivity also render AZO layer as an ideal candidate for transparent conductive electrodes, which enables a simplified cell structure featuring glass/AZO/perovskite/Spiro-OMeTAD/Au. Optimization of the perovskite layer leads to an excellent and repeatable photovoltaic performance, with the champion cell exhibiting an open-circuit voltage (V oc) of 0.94 V, a short-circuit current (J sc) of 20.2 mA cm–2, a fill factor (FF) of 0.67, and an overall power conversion efficiency (PCE) of 12.6% under standard 1 sun illumination. It was also revealed by steady-state and time-resolved photoluminescence that the AZO/perovskite interface resulted in less quenching than that between perovskite and hole transport material.
The recently explored FeNb11O29 is an advanced anode material for lithium‐ion batteries, owing to its high specific capacity and safety. However, it suffers from poor rate capability. To tackle this ...issue, a crystal structure modification is employed. Defective FeNb11O29 (FeNb11O27.9) is fabricated by using a one‐step solid‐state reaction method in N2. FeNb11O27.9 has the same orthorhombic shear ReO3 crystal structure (Amma space group) as FeNb11O29, but a larger unit‐cell volume and 3.8 % O2− vacancies (vs. all O2− ions), which improve the Li+‐ion diffusion coefficient by a factor of 88.3 %. The contained Nb4+ ions with free 4d electrons significantly increase the electronic conductivity by three orders of magnitude. Consequently, FeNb11O27.9 shows improved pseudocapacitive behavior and electrochemical properties. In comparison with FeNb11O29, FeNb11O27.9 exhibits a higher reversible capacity of 270 mAh g−1 with a higher first‐cycle coulombic efficiency of 90.6 % at 0.1 C. At 10 C, FeNb11O27.9 still retains a high capacity of 145 mAh g−1 with low capacity loss of 6.9 % after 200 cycles, in contrast to the values of 99 mAh g−1 and 11.1 % obtained for FeNb11O29.
Driving success: Oxygen‐deficient FeNb11O29 exhibits superior properties in terms of increased electronic conductivity, enhanced Li+‐ion diffusion coefficient, significant pseudocapacitive behavior, high reversible capacity, safe working potential, advanced first‐cycle coulombic efficiency, outstanding rate capability, and good cyclic stability. Therefore, it may be a promising anode material for high‐performance lithium‐ion batteries in electric vehicles.
Bone disease and disorder treatment might be difficult because of its complicated nature. Millions of patients each year need bone substitutes that may help them recover quickly from a variety of ...illnesses. Synthetic bone replacements that mirror the structural, chemical, and biological features of bone matrix structure will be very helpful and in high demand. In this research, the inorganic bioactive glass nanoparticles matrixed with organic collagen and silk fibroin structure (COL/SF/CaO-SiO2) were used to create multifunctional bone-like fibers in this study, which we describe here. The fiber structure is organized in a layered fashion comparable to the sequence in which apatite and neo tissue are formed. The amino groups in COL and SF combined with CaO-SiO2 to stabilize the resulting composite nanofiber. Morphological and functional studies confirmed that crystalline CaO-SiO2 nanoparticles with average sizes of 20 ± 5 nm are anchored on a 115 ± 10 nm COL/SF nanofiber matrix. X-ray photoelectron spectroscopic (XPS) results confirmed the presence of C, N, O, Ca, and Si in the composite fiber with an atomic percentage of 59.46, 3.30, 20.25, 3.38 and 13.61%. respectively. The biocompatibility examination with osteoblast cells (Saos-2) revealed that the CAL/SF/CaO-SiO2 composite nanofiber had enhanced osteogenic activity. Finally, when the CAL/SF/CaO-SiO2 composite nanofiber scaffolds were used to treat an osteoporotic bone defect in a rat model, the composite nanofiber scaffolds significantly promoted bone regeneration and vascularization. This novel fibrous scaffold class represents a potential breakthrough in the design of advanced materials for complicated bone regeneration.
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Ti2Nb10O29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate ...capability. To tackle this issue, a Cr3+–Nb5+ co-doping is employed, and a series of CrxTi2–2xNb10+xO29 compounds are prepared. The co-doping does not change the Wadsley–Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li+-ion diffusion coefficients. Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties. During the first cycle at 0.1 C, the optimized Cr0.6Ti0.8Nb10.6O29 sample delivers a large reversible capacity of 322 mAh g−1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g−1, while that of Ti2Nb10O29 is only 80 mAh g−1. Furthermore, Cr0.6Ti0.8Nb10.6O29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.
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•CrxTi2–2xNb10+xO29 compounds (0 ≤ x ≤ 0.6) are systematically and intensively studied.•Cr3+–Nb5+ co-doping increases the unit-cell volume and decreases the particle size.•CrxTi2–2xNb10+xO29 has large electronic conductivity and Li+ diffusion coefficient.•CrxTi2–2xNb10+xO29 has a large capacity, outstanding rate and cyclic properties.•Cr0.6Ti0.8Nb10.6O29 is promising for lithium-ion batteries of electric vehicles.
The preparation of ultra-high-performance concrete (UHPC) with both high-early-strength and good workability contributes to further promotion of its development and application. This study ...investigated the effects of different accelerators (SM, alkaline powder accelerator; SF, alkaline powder accelerator containing fluorine; and AF, alkali-free liquid accelerator containing fluorine) on the workability and strength properties of UHPC. The microstructure of UHPC was also characterized by using XRD and SEM. Several dosage levels of accelerators (2%, 4%, 6%, and 8% by mass) were selected. The results indicate that the setting time and fluidity of UHPC are gradually decreased with an increase in accelerators dosage. Compared with fluorine-containing SF/AF, fluorine-free SM evidently facilitates UHPC early strength gain speed. However, the fluorine-containing accelerators have a higher 28 d strength ratio, especially AF. The maximum compressive and flexural strength ratios are obtained at a dosage of 6%, which are 95.5% and 98.3%, respectively. XRD and SEM tests further reveal the effect of different accelerators on the macroscopic properties of UHPC from the micro level.
Cordierite-bonded porous SiC membrane supports with diatomite as silicon source were prepared in air at 1150–1400°C via reaction bonding technique. The phase composition, microstructure, flexural ...strength, open porosity, pore size distribution as well as dielectric properties of membrane supports were investigated as a function of the mass ratio of different starting materials, sintering temperature, graphite content and holding time. It was found that the diatomite addition strongly promoted the phase transformation towards cordierite, meanwhile, due to the enhancement of necks at the contacting pionts growth by the additions of diatomite (5.17wt%), a high three-point flexural strength of 49.19MPa was achieved at an open porosity of 37.72% sintered at 1250°C for 3h. Meanwhile, the cordierite structure can incorporate of diatomite (like Fe2O3) by solid solution formation, which can highly enhance on the electrical properties of cordierite-bonded SiC porous ceramics.
Inverted perovskite solar cells (PSCs) have been becoming more and more attractive, owing to their easy-fabrication and suppressed hysteresis, while the ion diffusion between metallic electrode and ...perovskite layer limit the long-term stability of devices. In this work, we employed a novel polyethylenimine (PEI) modified cross-stacked superaligned carbon nanotube (CSCNT) film in the inverted planar PSCs configurated FTO/NiO x /methylammonium lead tri-iodide (MAPbI3)/6, 6-phenyl C61-butyric acid methyl ester (PCBM)/CSCNT:PEI. By modifying CSCNT with a certain concentration of PEI (0.5 wt %), suitable energy level alignment and promoted interfacial charge transfer have been achieved, leading to a significant enhancement in the photovoltaic performance. As a result, a champion power conversion efficiency (PCE) of ∼11% was obtained with a V oc of 0.95 V, a J sc of 18.7 mA cm–2, a FF of 0.61 as well as negligible hysteresis. Moreover, CSCNT:PEI based inverted PSCs show superior durability in comparison to the standard silver based devices, remaining over 85% of the initial PCE after 500 h aging under various conditions, including long-term air exposure, thermal, and humid treatment. This work opens up a new avenue of facile modified carbon electrodes for highly stable and hysteresis suppressed PSCs.
We report herein perovskite solar cells using solution-processed silver nanowires (AgNWs) as transparent top electrode with markedly enhanced device performance, as well as stability by evaporating ...an ultrathin transparent Au (UTA) layer beneath the spin-coated AgNWs forming a composite transparent metallic electrode. The interlayer serves as a physical separation sandwiched in between the perovskite/hole transporting material (HTM) active layer and the halide-reactive AgNWs top-electrode to prevent undesired electrode degradation and simultaneously functions to significantly promote ohmic contact. The as-fabricated semitransparent PSCs feature a V oc of 0.96 V, a J sc of 20.47 mA cm–2, with an overall PCE of over 11% when measured with front illumination and a V oc of 0.92 V, a Jsc of 14.29 mA cm–2, and an overall PCE of 7.53% with back illumination, corresponding to approximately 70% of the value under normal illumination conditions. The devices also demonstrate exceptional fabrication repeatability and air stability.
α-Ag2S, with a direct forbidden bandgap of about 1.0 eV, is a non-toxic low bandgap semiconductor which can readily be deposited in the form of a thin film by chemical bath deposition. In a solar ...cell configuration, it can potentially provide a high short-circuit current due to the infrared absorption, and is compatible with the polysulfide electrolyte. Its practical use in a solar cell depends, however, critically on band alignment between the Ag2S, the oxide anode and the electrolyte redox potential. Here we examine the conduction band (CB) offsets in the nanostructured α-Ag2S sensitized TiO2 and SnO2 electrodes by X-ray Photoelectron Spectroscopy, and show that they can significantly differ from the extrapolated bulk values. The much higher CB offset for SnO2/Ag2S interface (∼0.6 eV) compared with that of ∼0.2 eV for TiO2/Ag2S, supplied a sufficient injection driving force and was favorable for the electron separation at the heterojunction. When fabricated into solar cells, a dramatically higher current density under AM 1.5 illumination for the SnO2/Ag2S heterojunction was obtained, which was contributed by the efficient electron injection.
•α-Ag2S serves as a promising candidate for non-toxic solar cell.•The energy level alignment between metal oxide and sensitizer is vital.•∼0.6 eV CB offset for SnO2/Ag2S supplied a sufficient injection driving force.•An impressive current density for SnO2/Ag2S based solar cell was obtained.
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