The deep-level traps at grain boundaries(GBs)and halide ion migration are quite challenging for further enhancement of the stability and efficiency of perovskite solar cells(PSCs)as well as for the elimination of noto...The deep-level traps at grain boundaries(GBs)and halide ion migration are quite challenging for further enhancement of the stability and efficiency of perovskite solar cells(PSCs)as well as for the elimination of notorious hysteresis.Herein,we report a large-sized strongly coordinated organic anion GB anchoring strategy for suppressing ion migration and passivating defects in planar PSCs.The practical implementation of this strategy involves the incorporation of potassium salts containing a large-sized organic counter anion(4-sulfobenzoic acid monopotassium salt,SAMS)into the perovskite precursor.It has been found that anions within SAMS can be firmly anchored at GBs due to the strong coordination interaction between C=O and/or S=O at both ends of bulky anion and undercoordinated Pb^(2+)and/or halide vacancies,along with the hydrogen bond between–OH and formamidinium.SAMS can not only passivate shallowlevel defects but also cause more effective passivation of the deep-level defects.The GB manipulation strategy results in a reduced defect density,an increased carrier lifetime as well as suppressed ion migration,which in turn contributed to enhanced efficiency and stability of PSCs together with a thorough elimination of hysteresis.As a result,the SAMSmodified device with an outstanding fill factor of 0.84 delivers a significant improvement in efficiency(22.7%)in comparison with the control device(20.3%).The unencapsulated modified device demonstrates only little degradation after 1320 h at 60℃.展开更多
Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries.Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-c...Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries.Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-containing poly(fluorenyl ether ketone)s(QA-OMPFEKs) were prepared from the(i) condensation polymerization of a newly developed octa-benzylmethyl-containing bisphenol monomer via Ullmann coupling,(ii) bromination at the benzylmethyl sites using N-bromosuccinimide, and(iii)quaternization of the bromomethyl groups using trimethylamine. The QA-OMPFEK-20 with an ion exchange capacity(IEC) of 1.66 mmolg^-1 exhibited a higher SO42-conductivity(9.62mScm^-1) than that of the QA-TMPFEK-40(4.82mScm^-1) at room temperature, which had a slightly higher IEC of 1.73 mmolg-1but much lower QA density.The enhanced SO42-conductivity of QA-OMPFEK-20 was attributed to the ion-segregated structure arising from the densely anchored QA groups, which was validated by SAXS observation. Furthermore, the QA-OMPFEK-20 showed much lower VO2+permeability(1.24×10^-14m^2s^-1) than QA-TMPFEK-40(5.40×10^-13m^2s^-1) and Nafion N212(5.36×10^-12m^2s^-1), leading to improved Coulombic and energy efficiencies in Vanadium redox flow batteries(VRFBs). Therefore, the Ullmann coupling extension is a valuable approach for the development of high performance anion exchange membranes for VRFBs.展开更多
A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)...A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)without ether bonds in the backbone and various quaternizing agents,including iodomethane,1-bromopentane,and(5-bromopentyl)-trimethylammonium bromide.The properties of the AEMs are investigated in terms of sulfuric acid doping content,swelling,vanadium permeability,ion selectivity,area-specific resistance,mechanical properties,VRFB performance,and cyclic testing.Particularly,a method of measuring the H^(+) permeability of the AEM is developed.It demonstrates that the poly(p-terphenyl-N-methylpiperidine)-quaternary ammonium(PTP-QA)membrane with a QA cation-tethered alkyl chain exhibits high H^(+) permeability,resulting in low area resistance.Combined with its low vanadium permeance,the PTP-QA membrane achieves nearly 370 times higher ion selectivity than Nafion 115.The VRFB based on PTP-QA-based AEM displays high Coulombic efficiencies above 99% at current densities of 80-160 mA cm^(-2).The higher energy efficiency of 89.8% is achieved at 100 mA cm^(-2)(vs.73.6% for Nafion 115).Meanwhile,the PTPQA-based AEM shows good cycling stability and capacity retention,proving great potential as the ion exchange membrane for VRFB applications.展开更多
Highly adhesive cold cathodes with high field emission performance are fabricated by using a screen-print- ing method. The emission density of carbon nanotube （CNT） cold cathode reaches 207.0 mA cm-2 at an electric ...Highly adhesive cold cathodes with high field emission performance are fabricated by using a screen-print- ing method. The emission density of carbon nanotube （CNT） cold cathode reaches 207.0 mA cm-2 at an electric field of 4.5 Vμm-1 under continuous driving mode, and high peak current emission of 315.8 mA corresponding to 4.5 A cm 2 at the electric field of 10.3 V μm-1 under pulsed driving mode. The emission patterns of the cold cathodes are of excellent uniformity that was revealed by vivid luminescent patterns of phosphor coated transparent indium tin oxide （ITO） an- ode. The cold cathodes also exhibit highly stable emission under continuous and pulsed driving modes. The high adhe- sion of CNTs to molybdenum substrates results in robust cold cathodes and is responsible for the high field emission performance. This robust CNT emitter could meet the operating requirements of continuous and pulsed electron sources, and it provides promising applications in various vacuum- micro/nanoelectronic devices.展开更多
The cationic group distribution along the polymeric backbones of anion exchange membranes(AEMs)has significant influence on their microscopic morphology and anion conductivity.To develop high-performance AEMs for vana...The cationic group distribution along the polymeric backbones of anion exchange membranes(AEMs)has significant influence on their microscopic morphology and anion conductivity.To develop high-performance AEMs for vanadium redox flow batteries(VRFBs),a series of poly(fluorenyl ether)samples bearing di-and tri-quaternary ammonium side chains with similar ion exchange capacities(IECs)were synthesized by grafting cationic alkyl chains with tertiary amine-containing poly(fluorenyl ether)precursors.The experimental results indicate that the introduction of the multi-cationic side chains facilitates the formation of micro-phase-separated morphologies and enhances anion conductivity.Moreover,the number of spacer atoms between the quaternary ammonium groups on the side chains affects the water uptake of the membranes,thus complicating the relationship between the density of cationic group distribution and anion conductivity.The poly(fluorenyl ether)s with dicationic side chains and six spacing atoms(DQA-PFE-C6)showed the highest anion conductivity.A VRFB assembled with DQA-PFE-C6 exhibited a maximum power density of 239.80 mW cm^−2 at 250 mA cm^−2,which is significantly higher than a VRFB assembled with Nafion 212.Therefore,side chain engineering is an effective chemical approach to enhance the properties of AEMs for VRFB applications.展开更多
基金the Support Plan for Overseas Students to Return to China for Entrepreneurship and Innovation(cx2020003)the Fundamental Research Funds for the Central Universities(2020CDJQY-A028 and 2020CDJ-LHZZ-074)the Natural Science Foundation of Chongqing(cstc2020jcyj-msxmX0629)。
文摘The deep-level traps at grain boundaries(GBs)and halide ion migration are quite challenging for further enhancement of the stability and efficiency of perovskite solar cells(PSCs)as well as for the elimination of notorious hysteresis.Herein,we report a large-sized strongly coordinated organic anion GB anchoring strategy for suppressing ion migration and passivating defects in planar PSCs.The practical implementation of this strategy involves the incorporation of potassium salts containing a large-sized organic counter anion(4-sulfobenzoic acid monopotassium salt,SAMS)into the perovskite precursor.It has been found that anions within SAMS can be firmly anchored at GBs due to the strong coordination interaction between C=O and/or S=O at both ends of bulky anion and undercoordinated Pb^(2+)and/or halide vacancies,along with the hydrogen bond between–OH and formamidinium.SAMS can not only passivate shallowlevel defects but also cause more effective passivation of the deep-level defects.The GB manipulation strategy results in a reduced defect density,an increased carrier lifetime as well as suppressed ion migration,which in turn contributed to enhanced efficiency and stability of PSCs together with a thorough elimination of hysteresis.As a result,the SAMSmodified device with an outstanding fill factor of 0.84 delivers a significant improvement in efficiency(22.7%)in comparison with the control device(20.3%).The unencapsulated modified device demonstrates only little degradation after 1320 h at 60℃.
基金supported by the National Natural Science Foundation of China (51503038)
文摘Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries.Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-containing poly(fluorenyl ether ketone)s(QA-OMPFEKs) were prepared from the(i) condensation polymerization of a newly developed octa-benzylmethyl-containing bisphenol monomer via Ullmann coupling,(ii) bromination at the benzylmethyl sites using N-bromosuccinimide, and(iii)quaternization of the bromomethyl groups using trimethylamine. The QA-OMPFEK-20 with an ion exchange capacity(IEC) of 1.66 mmolg^-1 exhibited a higher SO42-conductivity(9.62mScm^-1) than that of the QA-TMPFEK-40(4.82mScm^-1) at room temperature, which had a slightly higher IEC of 1.73 mmolg-1but much lower QA density.The enhanced SO42-conductivity of QA-OMPFEK-20 was attributed to the ion-segregated structure arising from the densely anchored QA groups, which was validated by SAXS observation. Furthermore, the QA-OMPFEK-20 showed much lower VO2+permeability(1.24×10^-14m^2s^-1) than QA-TMPFEK-40(5.40×10^-13m^2s^-1) and Nafion N212(5.36×10^-12m^2s^-1), leading to improved Coulombic and energy efficiencies in Vanadium redox flow batteries(VRFBs). Therefore, the Ullmann coupling extension is a valuable approach for the development of high performance anion exchange membranes for VRFBs.
基金supported by the National Natural Science Foundation of China(51603031)the Fundamental Research Funds for the Central Universities of China(N2005026)+1 种基金Liaoning Provincial Natural Science Foundation of China(20180550871 and 2020-MS-087)the Innovation Fund Denmark(DanFlow)。
文摘A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)without ether bonds in the backbone and various quaternizing agents,including iodomethane,1-bromopentane,and(5-bromopentyl)-trimethylammonium bromide.The properties of the AEMs are investigated in terms of sulfuric acid doping content,swelling,vanadium permeability,ion selectivity,area-specific resistance,mechanical properties,VRFB performance,and cyclic testing.Particularly,a method of measuring the H^(+) permeability of the AEM is developed.It demonstrates that the poly(p-terphenyl-N-methylpiperidine)-quaternary ammonium(PTP-QA)membrane with a QA cation-tethered alkyl chain exhibits high H^(+) permeability,resulting in low area resistance.Combined with its low vanadium permeance,the PTP-QA membrane achieves nearly 370 times higher ion selectivity than Nafion 115.The VRFB based on PTP-QA-based AEM displays high Coulombic efficiencies above 99% at current densities of 80-160 mA cm^(-2).The higher energy efficiency of 89.8% is achieved at 100 mA cm^(-2)(vs.73.6% for Nafion 115).Meanwhile,the PTPQA-based AEM shows good cycling stability and capacity retention,proving great potential as the ion exchange membrane for VRFB applications.
基金supported by the National Natural Science Foundation of China(51002161)One-Three-Five Strategic Planning of Chinese Academy of Sciences
文摘Highly adhesive cold cathodes with high field emission performance are fabricated by using a screen-print- ing method. The emission density of carbon nanotube （CNT） cold cathode reaches 207.0 mA cm-2 at an electric field of 4.5 Vμm-1 under continuous driving mode, and high peak current emission of 315.8 mA corresponding to 4.5 A cm 2 at the electric field of 10.3 V μm-1 under pulsed driving mode. The emission patterns of the cold cathodes are of excellent uniformity that was revealed by vivid luminescent patterns of phosphor coated transparent indium tin oxide （ITO） an- ode. The cold cathodes also exhibit highly stable emission under continuous and pulsed driving modes. The high adhe- sion of CNTs to molybdenum substrates results in robust cold cathodes and is responsible for the high field emission performance. This robust CNT emitter could meet the operating requirements of continuous and pulsed electron sources, and it provides promising applications in various vacuum- micro/nanoelectronic devices.
基金the National Natural Science Foundation of China(51873037 and 51503038)。
文摘The cationic group distribution along the polymeric backbones of anion exchange membranes(AEMs)has significant influence on their microscopic morphology and anion conductivity.To develop high-performance AEMs for vanadium redox flow batteries(VRFBs),a series of poly(fluorenyl ether)samples bearing di-and tri-quaternary ammonium side chains with similar ion exchange capacities(IECs)were synthesized by grafting cationic alkyl chains with tertiary amine-containing poly(fluorenyl ether)precursors.The experimental results indicate that the introduction of the multi-cationic side chains facilitates the formation of micro-phase-separated morphologies and enhances anion conductivity.Moreover,the number of spacer atoms between the quaternary ammonium groups on the side chains affects the water uptake of the membranes,thus complicating the relationship between the density of cationic group distribution and anion conductivity.The poly(fluorenyl ether)s with dicationic side chains and six spacing atoms(DQA-PFE-C6)showed the highest anion conductivity.A VRFB assembled with DQA-PFE-C6 exhibited a maximum power density of 239.80 mW cm^−2 at 250 mA cm^−2,which is significantly higher than a VRFB assembled with Nafion 212.Therefore,side chain engineering is an effective chemical approach to enhance the properties of AEMs for VRFB applications.
