Journal of Materials Chemistry A
·
2020
·Vol. 9
·期 1
·413-422
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IF 11.301
Xiaohuan Chang,Junjie Fu,Dongxing Kou,Wenhui Zhou,Zhengji Zhou,Shengjie Yuan,Yafang Qi,Zhi Zheng,Sixin Wu
The introduction of alkali metal (AM) post-deposition treatment (PDT) has led to the consecutive breakthrough of world record efficiencies for Cu(In,Ga)Se2 photovoltaics. However, for the derivative Cu2SnZn(S,Se)4 (CZTSSe) solar cells, the corresponding verdict seems partially unjustified due to the difference in defect chemical environment and phase structure, and the most effective incorporation means of AMs is still a mystery. In this work, for the first time, we developed a dual AM synergistic incorporation strategy combining light and heavy AMs by post-depositing CsF after NaF-PDT to improve the efficiency of CZTSSe solar cells. The relevant microscopic-electrical advantages with regard to the different roles of NaF and CsF PDT are discussed in more detail. It was found that the Na atoms are randomly dispersed both in the grain interior (GI) and grain boundaries (GBs), significantly increasing the acceptor concentration and passivating the deep level defects to enhance the Voc. In contrast, the Cs atoms are mainly segregated at the GBs, primarily increasing the potential of the GBs and improving the FF. The prominent electric benefits of Cs at the GBs and Na in the GI finally increase the device efficiency from 10.12% to 12.16%. Our findings solve the difficulty in obtaining the available Voc and FF for future high efficiency research and should serve as a basis for the in-depth understanding of AM-PDT in kesterite photovoltaics.
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JOURNAL OF ALLOYS AND COMPOUNDS
·
2020
·
IF 4.65
Xinyi Zhang,Jian-Feng Sun
An intriguing novel perovskite-type Cs 4 Mg 3 CaF 12 : Eu 2+ phosphor with desirable properties for potential application in the field of white light-emitting diodes was first time synthesized. The Rietveld structural refinement, scanning electron microscopy and high resolution transmission electron microscopy were used to determine the crystallographic parameters, morphology and microstructure of Cs 4 Mg 3 CaF 12 : Eu 2+ phosphor. The first principle calculation based on the density functional theory further provided a theoretical understanding of the band structure for the undoped Cs 4 Mg 3 CaF 12 and indicated that it has a large direct band gap of 7.1 eV. Upon the excitation of Cs 4 Mg 3 CaF 12 : Eu 2+ phosphor in the broad range of 250–450 nm, the bright blue light emission was observed with the maximum at 474 nm and a full width at half-maximum of 2808 cm −1 that was attributed to the electric-dipole allowed 4f 6 5 d 1 →4f 7 transition of Eu 2+ ions. Based on the Dexter’s theory, the concentration quenching mechanism among Eu 2+ in the Cs 4 Mg 3 CaF 12 : Eu 2+ phosphor was validated to be the dipole-dipole interaction, and the critical distance was determined to be 23.34 Å. On the basis of temperature-dependent luminescence measurement, an analysis of the origins of thermal quenching behavior was presented. The Cs 4 Mg 3 CaF 12 : Eu 2+ phosphor not only has favorable thermal stability with emission intensity reduction by 20% at T = 473 K in reference to the room temperature level, but also shows the integrated PL intensity 95% as high as that of BaMgAl 10 O 17 : Eu 2+ , internal quantum efficiency of 64% and color purity of 85%. The results of this work indicate that the blue-emitting Cs 4 Mg 3 CaF 12 : Eu 2+ phosphor with promising luminescence properties has a capacity for incorporation as a component to the near-UV based phosphor-converted WLEDs.
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SOLID STATE IONICS
·
2020
·
IF 3.107
Chang Su,Pengju Guo,Lihuan Xu
The Li (tri-(4-carboxyphenyl) amine) (Li-TCPA 2 ) doped polypyrrole (PPy-Li-TCPA 2 ) composites were successfully prepared by in-situ chemical oxidation using pyrrole and Li-TCPA 2 as raw materials. The structure, morphology, electrochemical properties of prepared materials were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), specific surface area test (BET), scanning electron microscopy (SEM), cyclic voltammogram (CV) and electrochemical impedance spectra (EIS), respectively. Also, the charge-discharge properties of the prepared composites were studied by galvanostatic charge-discharge testing. The results demonstrated that as-prepared composite material exhibited a reversible redox process at 2.0–4.0 V. And the discharge specific capacity for PPy-Li-TCPA 2 (2:1) and PPy-Li-TCPA 2 (6:1) are 50.4 mAh·g −1 and 63.7 mAh·g −1 as measured at 30 mA·g −1 between 2.0 and 4.0 V, while PPy-Li-TCPA 2 (4:1) exhibited the discharge specific capacity of 91.1 mAh·g −1 , which were remarkably higher than that of the pure PPy (29.5 mAh·g −1 ) under the same experimental conditions. At the same time, PPy-Li-TCPA 2 (4:1) has improved rate performance and stable cycleability. The excellent electrochemical properties are attributed to the introduction of Li-TCPA 2 as dopant , which improved the electrical conductivity and the redox activity of PPy. Furthermore, the resulted well-dispersed particle structure of the composite as well as its improved specific surface area for doped PPy facilitated to the contact of the electrolyte with the active material, leading to the increased utilization ratio of active material and the enhanced electrochemical performances .
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CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Zhihai Wu,Bintao Du,Guodong Tong,Hao Zhang,Yichen Zhang,Jun Xia,Zhenfu Zhao
Externally stimulated fluorescent materials have attracted widespread attention in the field of information security, but there are few reports on reversible hydrochromic materials, and the photoluminescence quantum yields (PL QYs) of these materials are still low. Herein, we report a strategy for encrypting/decrypting crucial information with Cd 2+ doped all-inorganic perovskite nanocrystals (PNCs) (Cd 2+ : CsPbX 3 , X = Cl, Br, I) anchored in magnesium silicate hollow spheres (MSHSs). The prepared Cd 2+ : CsPbX 3 -MSHSs micro-nanocomposites exhibit higher PL QYs due to the suppression of non-radiative decay and the enhanced radiative decay rate. Additionally, the layered structure of MSHSs limits the spatial distribution of PNCs, so the humidification/dehumidification process could result in optical signal reversible switching with high brightness and stability. We demonstrated that under the synergy of Cd 2+ ions doping and magnesium silicate matrix encapsulation, the micro-nanocomposites not only possess excellent and repeatable hydrochromic property, but also display remarkable photostability and thermal stability, which can be used for encryption and decryption of crucial information.
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ACS Applied Materials & Interfaces
·
2021
·
IF 9.229
Chunyan Wang,Jihuai Wu,Shibo Wang,Xuping Liu,Xiaobing Wang,Zhongliang Yan,Liqiang Chen,Xiao Liu,Guodong Li,Weihai Sun,Zhang Lan
The practical applications of perovskite solar cells (PSCs) are limited by further improvement of their stability and performance. Additive engineering and interface engineering are promising medicine to cure this stubborn disease. Herein, an alkali metal fluoride as an additive is introduced into the tin oxide (SnO2) electron transport layer (ETL). The formation of coordination bonds of F– ions with the oxygen vacancy of Sn4+ ions decreases the trap-state density and improves the electron mobility; the hydrogen bond interaction between the F ion and amine group (FA+) of perovskite inhibits the diffusion of organic cations and promotes perovskite (PVK) stability. Meanwhile, the alkali metal ions (K+, Rb+, and Cs+) permeated into PVK fill the organic cation vacancies and ameliorate the crystal quality of PVK films. Consequently, a SnO2-based planar PSC exhibits a power conversion efficiency (PCE) of 20.24%, while the PSC modified by CsF achieves a PCE of 22.51%, accompanied by effective enhancement of stability and negligible hysteresis. The research results provide a typical example for low-cost and multifunctional additives in high-performance PSCs.
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MACROMOLECULES
·
2019
·
IF 5.997
Chao Qian,Runxin Bei,Tianwen Zhu,Weiwen Zheng,Siwei Liu,Zhenguo Chi,Matthew. P. Aldred,Xudong Chen,Yi Zhang,Jiarui Xu
An original design strategy for the preparation of polymers with a low dielectric constant is presented. The key to this design strategy is taking the most advantage of the secondary relaxation behavior of the polymer chains to obtain more free volume in the bulk, which can effectively reduce the dielectric constant of the polymer. By using this design strategy, we have successfully synthesized a novel polyimide TmBPHF with a pendant group that consists of a biphenyl unit attached to the meta-position of a phenyl ring that is part of a triaryl unit. The intrinsic k and dielectric loss values of the TmBPHF are 2.09 and 0.0012 at 10 kHz, respectively. More importantly, such outstanding low-k performance remains stable up to 300 °C. The excellent low-k performance of TmBPHF is mainly due to the secondary relaxation, especially the β relaxation, which occurs from the rotation of the pendant group. The TmBPHF film shows an ultralow moisture rate (∼0.17%), which is able to maintain the low-k property stability in different humid environments. Meanwhile, the TmBPHF film also shows excellent thermal stability and excellent mechanical properties, with a glass transition temperature (Tg) of 302 °C, 5 wt % decomposition temperature (Td5%) of 549 °C, and residual of 70% at 800 °C under N2. The tensile strength and tensile modulus of the polyimide film are equal to 85.8 MPa and 2.02 GPa, respectively. In addition, the TmBPHF film is soluble in common solvents, which allows simple solution processing and efficient, low-cost, and continuous roll-to-roll processes. The design strategy is beneficial for lowering the k value and simultaneously maintaining the overall properties of polyimides, which possibly could also be extended to other novel high-performance polymer systems.
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CHINESE JOURNAL OF POLYMER SCIENCE
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2019
·Vol. 38
·期 3
·213-219
·
IF 2.804
Qian Chao,Fan Zhen-Guo,Zheng Wei-Wen,Bei Run-Xin,Zhu Tian-Wen,Liu Si-Wei,Chi Zhen-Guo,Aldred Matthew P.,Chen Xu-Dong,Zhang Yi,Xu Jia-Rui
High-performance low- k and low-loss circuit materials are urgently needed in the field of microelectronics due to the upcoming Fifth-Generation Mobile Communications Technology (5G Technology). Herein, a facile design strategy for non-fluorinated intrinsic low- k and low-loss polyimides is reported by fully considering the secondary relaxation behaviors of the polymer chains. A new amorphous non-fluorinated polymer (TmBPPA) with a k value of 2.23 and a loss tangent lower than 3.94 × 10 −3 at 10 4 Hz has been designed and synthesized, which to the best of our knowledge is the lowest value amongst the non-fluorinated and non-porous polymers reported in literature. Meanwhile, TmBPPA exhibits excellent overall properties, such as excellent thermostability, good mechanical properties, low moisture absorption, and high bonding strength. As high-performance flexible circuit materials, all these characteristics are highly expected to meet the present and future demands for high density, high speed, and high frequency electronic circuit used in 5G wireless networks.
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INORGANIC CHEMISTRY
·
2018
·
IF 4.7
Chunyan Jiang,Mingying Peng,Alok M. Srivastava,Lihua Li,Mikhail G. Brik
Narrow band red-emitting Mn4+-doped fluoride phosphor is an essential red component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+ and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+ phosphor as the red component. Our results not only reveal that a high-performance Mn4+ red phosphor is achieved through cationic substitutions but also construct a relationship of performance–structure to guide the design of Mn4+ phosphors in the future.
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ChemElectroChem
·
2019
·Vol. 6
·期 10
·2707-2714
·
IF 3.975
Dan Li,Zhixiang Zeng,Di Lu,Feng Nie,Lele Wen,Lijing Zhu
Graphical Ask the conductor :A polyanionic perfluoroimide-based conducting Li salt (LiPFSDI) is synthesized and blended with polyethylene oxide (PEO) to fabricate the polymer electrolyte membrane. The PEO-LiPFSDI composite electrolyte exhibits high ionic conductivity, a wide electrochemical window (up to 6 V versus Li + /Li), high t Li + (0.89), and excellent cycling performance. Fluorosulfonimide lithium salts have been widely used as conductors in solid polymer electrolytes for solid Li-ion batteries (LIBs). However, low conductivity and poor compatibility with the polymer host (usually polyethylene oxide, PEO) remain challenges in the design of these salts. In this paper, we synthesized a highly Li + -conductive salt containing the poly(perfluoroalkylsulfonyl)diimide (PFSDI − ) dianion for the first time. LiPFSDI represents the first example of a single Li-ion-conducting polymer (SLICP) with a conjugated sulfonimide moiety (−SO 2 −N (−) −SO 2 −N (−) −SO 2 −). The PEO−LiPFSDI blend electrolyte exhibits significant enhancements in ionic conductivity (2.24×10 −4 S cm −1 at 80 °C)and electrochemical stability (up to 6 V vs. Li + /Li). A prototype LiFePO 4 /Li battery with the PEO−LiPFSDI composite electrolyte shows excellent cycling performance with a high reversible capacity of 148 mAh g −1 at a rate of 0.1 C and 135 mAh g −1 at 0.2 C (70 °C), and maintains 100 stable cycles for over 1500 hours.
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LIQUID CRYSTALS
·
2014
·
IF 2.349
Shiming Gong,Ming Liu,Zhen Sun,Senlin Xia,Yinghan Wang
A new triphenylamine-based functional diamine monomer named N, N-bis (4-aminophenyl)-4-(nonyloxy-biphenyl)-4′-aminophenyl ether (N9) was successfully synthesised from cesium fluoride-mediated N,N-diarylation of 4-(nonyloxy-biphenyl)-4′-aminophenyl ether with p-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. A series of polyimides (PIs) with triphenylamine (TPA) moieties were prepared from the newly synthesised diamine monomer, 3,3′-dimethyl-4,4′-methylene-dianiline and 4,4′-oxydiphthalic anhydride through a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. The PIs were completely amorphous and exhibited good solubility in organic solvents. PI films attained from a casting method showed high transmittance above 90% in the wave length range of 400–700 nm and could align liquid crystals vertically before and after rubbing treatment. The PIs derived from N9 exhibited much higher thermal stability compared with the corresponding PIs from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (D12). The results demonstrated that the introduction of TPA units into the polymer backbone could largely enhance the thermal stability of PIs while sustaining its solubility.
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POLYMER INTERNATIONAL
·
2015
·Vol. 64
·期 12
·1715-1721
·
IF 2.409
Tao Xing,Kai Zhang
Novel carborane polyimides were synthesized and studied. Aromatic meta -carborane diamines of different structures were initially prepared. Polymerization of these new diamines with the commercially available 4,4′-oxydiphthalic dianhydride led to meta -carborane polyimides with various structures and thermal properties. The amorphous polymers obtained are of moderate molecular weight and show good solubility in organic solvents. Thermal analyses of these polyimides reveal that they have moderate to ultrahigh thermal stability depending on their specific structures, with 5% decomposition temperatures ranging from 382 to 786 °C in nitrogen. Different thermal properties of these polyimides are observed when the analyses are performed in dry air, with 5% decomposition temperatures shifting to temperatures ranging from 388 to 1128 °C. Due to the ever-present requirement of higher performance polymers in fields like aerospace and defense, the methods developed here could be an impetus for the development of these industries. © 2015 Society of Chemical Industry
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LIQUID CRYSTALS
·
2016
·
IF 2.244
Qing Gong,Xinguo Zheng,Shiming Gong,Heng Zhang,Lulu Liu,Yinghan Wang
A novel functional diamine N12, containing triphenylamine moiety, biphenyl, tert-butyl substituents and long alkyl chain, N,N-bis(4-aminophenyl)-p-(3,5-di-tert-butyl-4-dodecyloxy phenyl) aniline (N12), was synthesised and characterised. A series of polyimides (PIs) were prepared based on 2,2ʹ-bis(trifluoromethyl)benzidine, 4,4ʹ-oxydiphthalicanhydride and different contents of N12 via a conventional two-step procedure that included a ring-opening polyaddition to gain polyamic acids, followed by chemical cyclodehydration. The chemical structures of the intermediates, diamines and PIs were characterised by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. All of the PIs were amorphous and exhibited good solubility in both polar aprotic solvents and some low boiling point solvents. PIs containing different content of N12 could induce highly uniform vertical alignment of liquid crystals (LCs). More importantly, PIs derived from N12 showed a good rubbing resistance. Besides, all PI films showed high transmittance in the wavelength range 400–700 nm and good thermal stabilities. Such PIs could be suitable candidates for alignment layers used in the manufacture of high-performance vertical alignment mode LC displays.
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危险品化学品经营许可证（带存储）