The conductivity of PEDOT:PSS films was significantly enhanced from 0.3 S cm−1 to 3065 S cm−1 through a treatment with dilute sulfuric acids. PEDOT:PSS films with a sheet resistance of 39 Ω sq−1 and ...transparency of around 80% at 550 nm are obtained. These PEDOT:PSS films with conductivity and transparency comparable to ITO can replace ITO as the transparent electrode of optoelectronic devices.
Realization of fast hole extraction is an effective route for the performance enhancement of inverted perovskite solar cells (PSCs). The precise bandgap tuning in perovskite layer has been expected ...to accelerate hole extraction. Therefore, in this report, we demonstrate a modified one-step fabrication method for the bandgap tuning of perovskite layer by designing iodide concentration gradient. Prior to the perovskite precursor solution spin-coated, different concentration of methanaminium iodide (MAI) solution was pre-coated on PEDOT:PSS layer to form iodide concentration gradient in perovskite layer. Fast hole extraction and short lifetime due to iodide concentration gradient was confirmed by photoluminescence measurement. By optimizing the MAI concentration with 4 mg/ml, the modified PSCs exhibited a power conversion efficiency of 16.67% due to an increase in short-circuit current density (Jsc) from 19.66 mA/cm2 to 23.52 mA/cm2 and an increase in open circuit voltage from 0.97 V to 1.01 V. These values are significantly higher than PSCs using conventional one-step fabrication method without pre-coated MAI layer, which exhibit efficiency of only 14.8%. We think that this new approach is an effective way to enhance the performance of PSCs.
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•A modified one-step spin coating method for perovskite solar cells fabrication was proposed.•An appropriate amount of methanaminium iodide (MAI) was spin-coated on PEDOT:PSS layer to form iodide concentration gradient in perovskite layer.•Fast hole extraction and short lifetime due to iodide concentration gradient was confirmed.
One of the long‐standing challenges of current lead‐free energy storage ceramics for capacitors is how to improve their comprehensive energy storage properties effectively, that is, to achieve a ...synergistic improvement in the breakdown strength (Eb) and the difference between maximum polarization (Pmax) and remnant polarization (Pr), making them comparable to those of lead‐based capacitor materials. Here, a polymorphic polar nanoregions (PNRs) structural design by first introducing 0.06 mol BaTiO3 into Bi0.5Na0.5TiO3 is proposed to construct the morphotropic phase boundary with coexisting structures of micrometer‐size domains and polymorphic nanodomains, enhance the electric field‐induced polarization response (increase Pmax). Then Sr(Al0.5Ta0.5)O3 (SAT)‐doped 0.94 Bi0.5Na0.5TiO3‐0.06BaTiO3 (BNBT) energy storage ceramics with polymorphic PNRs structures are synthesized following the guidance of phase‐field simulation and rational composition design (decrease Pr). Finally, a large recoverable energy density (Wrec) of 8.33 J cm−3 and a high energy efficiency (η) of 90.8% under 555 kV cm−1 are obtained in the 0.85BNBT‐0.15SAT ceramic prepared by repeated rolling process method (enhance Eb), superior to most practical lead‐free competitors increased consideration of the stability of temperature (a variation <±6.2%) and frequency (Wrec > 5.0 cm−3, η > 90%) at 400 kV cm−1. This strategy provides a new conception for the design of other‐based multifunctional energy storage dielectrics.
Polymorphic polar nanoscale design and grain size engineering are proposed to achieve a synergistic improvement in the breakdown strength and the difference between maximum polarization and remnant polarization. An improved recoverable energy density of 8.33 J cm−3 and a high energy efficiency of 90.8% are simultaneously obtained under the electric field of 555 kV cm−1 in Bi0.5Na0.5TiO3‐based relaxor ferroelectric ceramics.
Solar evaporation is considered a promising technology to address the issue of fresh water scarcity. Although many efforts have been directed towards increasing the solar–thermal conversion ...efficiency, there remain challenges to develop efficient and cost‐effective solar–thermal materials from readily available raw materials. Furthermore, further structural modification of the original biomass structure, particularly at multiple length scales, are seldom reported, which may further improve the solar–thermal performance of these material systems. Herein, a novel low‐cost system is developed based on a common bio‐waste, pomelo peels (PPs), through a bioinspired fractal structural design strategy, fractal carbonized pomelo peels (FCPP). This FCPP system shows an extremely high solar spectrum absorption of ≈98%, and marvelous evaporation rate of 1.95 kg m−2 h−1 with a solar–thermal efficiency of 92.4%. In addition, the mechanisms of the evaporation enhancement by fractal structural design are identified by numerical and experimental methods. Moreover, using FCPP in solar desalination shows great superiority in terms of cost and its potential in sewage treatment is also studied. The present work is an insightful attempt on providing a novel proposal to develop bio‐waste‐derived solar–thermal materials and construct biomimetic structures for efficient solar evaporation and applications.
A novel low‐cost system based on a common bio‐waste, pomelo peels, through a bioinspired fractal structural design strategy, fractal carbonized pomelo peel, are developed. The system shows a marvelous evaporation rate of 1.95 kg m‐2 h‐1 with a solar‐thermal efficiency of 92.4%. Furthermore, the mechanisms of the evaporation enhancement by fractal structural design are identified via numerical and experimental methods.
The mechanisms underpinning high energy storage density in lead-free Ag1–3xNdxTayNb1-yO3 antiferroelectric (AFE) ceramics have been investigated. Rietveld refinements of in-situ synchrotron X-ray ...data reveal that the structure remains quadrupled and orthorhombic under electric field (E) but adopts a non-centrosymmetric space group, Pmc21, in which the cations exhibit a ferrielectric configuration. Nd and Ta doping both stabilize the AFE structure, thereby increasing the AFE-ferrielectric switching field from 150 to 350 kV cm−1. Domain size and correlation length of AFE/ferrielectric coupling reduce with Nd doping, leading to slimmer hysteresis loops. The maximum polarization (Pmax) is optimized through A-site aliovalent doping which also decreases electrical conductivity, permitting the application of a larger E. These effects combine to enhance energy storage density to give Wrec = 6.5 J cm−3 for Ag0.97Nd0.01Ta0.20Nb0.80O3.
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Schematic diagram illustrating how energy storage density is optimized through doping in AgNbO3 and shedding light on the design of novel antiferroelectric (AFE) materials with excellent energy storage density.
●Excellent performance achieved for AgNbO3-based antiferroelectric lead-free energy storage ceramics.●The first observation of a field induced ferrielectric phase.●4 principles proposed for the design of high energy density properties of AgNbO3-based antiferroelectric ceramics: i) increased resistivity, ii) optimization of maximum polarization, iii) decreased antipolar/polar coupling, and iv) enhanced AFE stability.
Starting from metal oxides, B4C and graphite, a suite of high-entropy boride ceramics, formulated (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2, (Hf0.2Zr0.2Mo0.2Nb0.2Ti0.2)B2 and (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2 ...derived from boro/carbothermal reduction at 1600 °C were fabricated by spark plasma sintering at 2000 °C. It was found that the synthetic high-entropy boride crystalized in hexagonal structure and the yield of the targeting phase was calculated to be over 93.0 wt% in the sintered ceramics. Benefitting from the nearly full densification (96.3% ˜ 98.5% in relative density) and the refined microstructure, the products exhibited the relatively high Vickers hardness. The indentation fracture toughness was determined to be comparable with the single transition metal-diboride ceramics. It should be noted that the formation of high-entropy boride ceramics were featured with the relatively high hardness at no expense of the fracture toughness.
Flexible and stretchable organic solar cells (OSCs) have attracted enormous attention due to their potential applications in wearable and portable devices. To achieve flexibility and stretchability, ...many efforts have been made with regard to mechanically robust electrodes, interface layers, and photoactive semiconductors. This has greatly improved the performance of the devices. State‐of‐the‐art flexible and stretchable OSCs have achieved a power conversion efficiency of 15.21% (16.55% for tandem flexible devices) and 13%, respectively. Here, the recent progress of flexible and stretchable OSCs in terms of their components and processing methods are summarized and discussed. The future challenges and perspectives for flexible and stretchable OSCs are also presented.
The recent progress in flexible and stretchable organic solar cells (OSCs) is discussed. For flexible OSCs, the features of the commonly used flexible transparent electrodes and the relevant performance are selectively summarized and discussed. For stretchable OSCs, both the nonintrinsic and intrinsic processing methods are presented and discussed.
Inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, I) have attracted enormous attention as a novel optoelectronic material with enhanced stability. However, the perovskite CsPbX3 thin ...films fabricated by one-step spin-coating method contain the defects of voids or pinholes, seriously affecting their amplified spontaneous emission (ASE) or lasing performance. To solve this issue, herein, we demonstrate that by simply introducing ZnO nanoparticles (NPs) into the CsPbBr3 precursor solution, the CsPbBr3:ZnO films synthesized by one-step spin-coating method exhibit enhanced crystallization, improved photoluminescence (PL) intensity and prolonged lifetime. Introducing the ZnO NPs can provide an effective route for CsPbBr3 nucleation during the spin-coating and annealing process, contributing to compact and smooth thin films with no obviously large voids or pinholes. Under the one-photon (400nm) and two-photon (800nm) femtosecond laser excitation, the ASE of CsPbBr3 and CsPbBr3:ZnO films have been investigated at room temperature, respectively. After the film compactness, surface smoothness and crystal size are modified by the ZnO additive, both the emission efficiency and the ASE threshold of the CsPbBr3:ZnO films have been improved in comparison with the pure CsPbBr3 films.
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•Efficient reduction of large voids or pinholes in CsPbBr3 films using ZnO NPs.•CsPbBr3:ZnO films exhibit improved PL intensity and prolonged lifetime.•ASE emission efficiency and ASE threshold of CsPbBr3:ZnO films are improved.
Thermoelectric materials can be used as the active materials in thermoelectric generators and as Peltier coolers for direct energy conversion between heat and electricity. Apart from inorganic ...thermoelectric materials, thermoelectric polymers have been receiving great attention due to their unique advantages including low cost, high mechanical flexibility, light weight, low or no toxicity, and intrinsically low thermal conductivity. The power factor of thermoelectric polymers has been continuously rising, and the highest ZT value is more than 0.25 at room temperature. The power factor can be further improved by forming composites with nanomaterials. This article provides a review of recent developments on thermoelectric polymers and polymer composites. It focuses on the relationship between thermoelectric properties and the materials structure, including chemical structure, microstructure, dopants, and doping levels. Their thermoelectric properties can be further improved to be comparable to inorganic counterparts in the near future.
Thermoelectric polymers have gained great attention, arising from their merits of low cost, light weight, low or no toxicity, and high mechanical flexibility. This article provides a review on the recent progress of thermoelectric polymers and composites.
This study aimed to investigate the effects of the original thickness on the densification, microstructure, and nanoindentation hardness of silicon carbide (SiC) ceramics prepared by the spark plasma ...sintering (SPS) process. The densification of SiC ceramics with different initial thicknesses ranging from 50 to 2000 µm was investigated in combination with varying SPS sintering temperature at 1700–1900°C. The results indicated that the densification of SiC sample with the initial thickness of 50 µm was complete after sintering at 1700°C. On the contrary, when the initial thickness exceeded 50 µm, it resulted in a porous microstructure. When the initial thickness varied from 50 to 100 µm, dense SiC monolithic could be obtained after sintering at 1800°C. All the samples were fully densified after sintering at 1900°C. The predominant factors for the thickness effect were mainly derived from the unique characteristics of SPS. The hardness of SiC ceramics was measured using nanoindentation, and it was found to have a strong correlation with the initial thickness, mainly attributed to the densification status. The dense SiC product demonstrated nanoindentation hardness with high values of ∼28.0 GPa.
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