In the context of global warming,escalating water cycles have led to a surge in drought frequency and severity.Yet,multidecadal fluctuations in drought and their multifaceted influencing factors remain inadequately un...In the context of global warming,escalating water cycles have led to a surge in drought frequency and severity.Yet,multidecadal fluctuations in drought and their multifaceted influencing factors remain inadequately understood.This study examined the multidecadal changes in drought characteristics(frequency,duration,and severity)and their geographical focal points within China's north-south transitional zone,the Qinling-Daba Mountains(QDM),from 1960 to 2017 using the Standardized Precipitation Evapotranspiration Index(SPEI).In addition,a suite of eight scenarios,correlation analysis,and wavelet coherence were used to identify the meteorological and circulation factors that influenced drought characteristics.The results indicate the following:(1)From 1960 to 2017,the QDM experienced significant interdecadal variations in drought frequency,duration,and severity,the climate was relatively humid before the 1990s,but drought intensified thereafter.Specifically,the 1990s marked the period of the longest drought duration and greatest severity,while the years spanning 2010 to 2017 experienced the highest frequency of drought events.(2)Spatially,the Qinling Mountains,particularly the western Qinling Mountain,exhibited higher drought frequency,duration,and severity than the Daba Mountains.This disparity can be attributed to higher rates of temperature increase and precipitation decrease in the western Qinling Mountain.(3)Interdecadal variations in droughts in the QDM were directly influenced by the synergistic effects of interdecadal fluctuations in air temperature and precipitation.Circulation factors modulate temperature and precipitation through phase transitions,thereby affecting drought dynamics in the QDM.The Atlantic Multidecadal Oscillation emerges as the primary circulation factors influencing temperature changes,with a mid-1990s shift to a positive phase favoring warming.The East Asian Summer Monsoon and El Ni?o-Southern Oscillation are the main circulation factors affecting precipitation changes,with positive pha展开更多
Recently,perovskite solar cells(PVSCs)based on CsPbI2Br have attracted increasing attention owing to their good balance between efficiency and stability.Solutionprocessed CsPbI2Br perovskites usually contain various d...Recently,perovskite solar cells(PVSCs)based on CsPbI2Br have attracted increasing attention owing to their good balance between efficiency and stability.Solutionprocessed CsPbI2Br perovskites usually contain various defects which need passivation for PVSCs with high-performance as well as good stability.Since the degradation of perovskite films usually begins at the grain boundaries,here we report a facile defect passivation strategy by spin-coating a KF solution on the CsPbI2Br perovskite surface.The deposited KF salt mostly locates at the grain boundaries of the perovskite surface,resulting in PVSCs with improved stability.Both steady-state and time-resolved photoluminescence results suggest that the defects of perovskite were significantly passivated by KF treatment.Consequently,the best-performance PVSC based on CsPbI2Br with KF treatment shows an enhanced power conversion efficiency(PCE)of 15.01%with a larger open circuit voltage(VOC)of 1.26 V in comparison with the pristine CsPbI2Br-based counterpart which exhibits an inferior PCE of 14.14%with a VOC of 1.18 V.展开更多
Comprehensive Summary,The development of novel building blocks with sp3-hybridized-carbon-free conjugated skeletons is important to further advance and enrich nonfullerene acceptors(NFAs),but this remains a challenge ...Comprehensive Summary,The development of novel building blocks with sp3-hybridized-carbon-free conjugated skeletons is important to further advance and enrich nonfullerene acceptors(NFAs),but this remains a challenge due to the lack of strategies to effectively modulate the aggregation behavior of resulting NFAs.Herein,two novel nitrogen-bridged octacyclic ladder-type heteroarenes end-capped with thiophene rings(BTPS)or selenophene rings(BTPSe)are designed and synthesized as the donor cores for constructing NFAs(MQX-2 and MQX-4).It is found that replacing the sulfur atoms(MQX-2)at the outer positions of the heteroarene core with selenium atoms(MQX-4)can effectively modulate the molecular packing mode of the NFAs.The incorporation of selenium atoms induces stronger O···Se noncovalent interaction than O···S,thus promoting the formation of mixed H/J-type aggregates in MQX-4.Benefiting from more electron hopping channels,MQX-4 exhibits higher electron transport(more than 1-fold enhancement)and photovoltaic properties compared to MQX-2,which forms only H-type aggregates.展开更多
Asymmetric nonfullerene acceptors(NFAs)possess larger dipole moments and stronger intermolecular bonding energy than their symmetric counterparts thereby making them promising candidates for high-performance polymer s...Asymmetric nonfullerene acceptors(NFAs)possess larger dipole moments and stronger intermolecular bonding energy than their symmetric counterparts thereby making them promising candidates for high-performance polymer solar cells(PSCs).Herein,we report twoefficient acceptor–donor–acceptor(A–D–A)type NFAs(M14 and M18)with asymmetric side chains that show enhanced intermolecular interactions compared with their corresponding counterparts(M17 and M19)based on symmetric side chains.Furthermore,M14 and M18 exhibit elevated lowest unoccupiedmolecular orbitals and smallerπ–πstacking distances in comparison with M17 and M19,respectively.In combination with the benchmark polymer donor of PM6,the PM6:M14 blend affords superior charge transport properties,and more importantly,an increased power conversion efficiency(PCE)of 15.49%in comparison with the M17-based counterpart(13.01%PCE).Similarly,the asymmetric M18-based blend also shows a higher PCE of 13.00%than the M19-based blend(11.55%).Through further interface engineering,the bestperforming M14-based device delivers an enhanced PCE of 16.46%,which represents a record value among all asymmetric A–D–A type NFAs.Our results provide new insights into the design of asymmetric NFAs with enhanced intermolecular interactions for highperformance PSCs.展开更多
Defect passivation is an important strategy to achieve perovskite solar cells(PVSCs) with enhanced power conversion efficiencies(PCEs) and improved stability because the trap states induced by defects in the interface...Defect passivation is an important strategy to achieve perovskite solar cells(PVSCs) with enhanced power conversion efficiencies(PCEs) and improved stability because the trap states induced by defects in the interfaces and grain boundaries of perovskites are harmful to both large open circuit voltage and high photocurrent of devices. Here, zinc cations(Zn^2+) were used as a dopant to passivate defects of the CsPbI2Br perovskite leading to Zn^2+-doped CsPbI2Br film with fewer trap states, improved charge transportation, and enhanced light-harvesting ability. Thus, the best-performance PVSC based on CsPbI2 Br with the optimal Zn^2+doping shows a higher PCE of 12.16% with a larger open-circuit voltage(VOC) of 1.236 V, an improved shortcircuit current(JSC) of 15.61 mA cm^-2 in comparison with the control device based on the pure CsPbI2Br which exhibits a PCE of 10.21% with a VOCof 1.123 V, a JSCof 13.27 mA cm^-2. Time-resolved photoluminescence results show that the Zn^2+doping leads to perovskite film with extended photoluminescence lifetime which means a longer diffusion length and subsequently enhanced photocurrent and open circuit voltage. This work provides a simple strategy to boost the performance of PVSCs through Zn^2+doping.展开更多
Controlling the aggregation of small-molecule acceptors(SMAs)is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells(PSCs).However,reducing intermolecular aggreg...Controlling the aggregation of small-molecule acceptors(SMAs)is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells(PSCs).However,reducing intermolecular aggregation of SMAs is usually accompanied by the disruption of compact molecular packing thereby leading to their decreased electron mobilities.Here,two novel M-series SMAs(MD1T and MD2T)based on ladder-type heterononacenes with neighboring side-chains separated by one or two thiophene rings are designed and synthesized.It is found that shortening the spacing of the neighboring side-chains of the SMAs can greatly alleviate the intermolecular aggregation and alter the molecular orientation from bimodal edge-on/face-on to predominant face-on while maintaining the compact molecular packing.As a result,a more favorable morphology with smaller domain sizes is formed for the MD1T-based blend films,which greatly improves the charge generation and charge transport for the corresponding PSCs.The best-performing MD1T-based device affords an efficiency of 12.43%,over seven times higher than that of the MD2T-based device.This work reveals the importance of the spacing between the neighboring side-chains in modulating the molecular aggregation and active layer morphology,and the obtained structure-performance relationships shall provide important guidance for designing highly efficient SMAs.展开更多
Optimal bulk-heterojunction(BHJ)morphology is crucial for efficient charge transport and good photovoltaic performance in organic solar cells(OSCs).Yet,the correlation between chemical structures of nonfullerene accep...Optimal bulk-heterojunction(BHJ)morphology is crucial for efficient charge transport and good photovoltaic performance in organic solar cells(OSCs).Yet,the correlation between chemical structures of nonfullerene acceptors(NFAs)and molecular interaction in the BHJ blends remains opaque.Herein,we study three isomeric NFAs referred to as MQ1-x(x=β,y,or 8)that shared an asymmetric selenophene-fused heteroheptacene backbone end-capped by two monochlorinated end groups.Remarkably,miscibility between the polymer donor of PM6 and MQ1-x successively elevates as the chlorine atoms move fromβ-,to y-,to 8-position of terminals.Combined with the varied molecular crystallinity of these NFAs,diverse BHJ morphologies are observed in their blend films.As a result,the MQ1-8-based devices present the highest PCE of 12.08%owing to the efficient charge dissociation and transport induced by the compact molecular packing and optimal BHJ morphology.Our investigation provides a new insight in the material design that has a good balance in molecular packing and film morphology for high-performance OSCs.展开更多
The development and deployment of diverse resistance sources in new wheat cultivars underpin the durable control of stripe rust.In the present study,two loci for adult plant resistance(APR),QYr SM155.1 and QYr SM155.2...The development and deployment of diverse resistance sources in new wheat cultivars underpin the durable control of stripe rust.In the present study,two loci for adult plant resistance(APR),QYr SM155.1 and QYr SM155.2,were identified in the Chinese wheat breeding line Shaanmai 155.QYr SM155.1 was mapped to a 3.0-c M interval between the single-nucleotide polymorphism(SNP)markers AX-109583610 and AX-110907562 on chromosome arm 2 BL.QYr SM155.2 was mapped to a 2.1-c M interval flanked by the SNP markers AX-110378556 and AX-86173526 on chromosome arm 7 AS.A genome-wide association study was used to identify markers associated with APR in a panel of 411 spring wheat lines.Thirteen and 11 SNPs were significantly associated with QYr SM155.1 and QYr SM155.2,respectively,corresponding to physical intervals of 653.75–655.52 Mb on 2 BL and 81.63–83.93 Mb on7 AS.To characterize the haplotype variation and the distribution of these QTL,haplotype analysis was performed based on these SNPs in an independent panel of 1101 worldwide wheat accessions.Three major haplotypes(2 B_h1,2 B_h2,and 2 B_h3)for QYr SM155.1 and four major haplotypes(7 A_h1,7 A_h2,7 A_h3,and 7 A_h4)for QYr SM155.2 were identified.Accessions individually harboring QYr SM155.1_h1 and QYr SM155.2_h1 haplotypes and their combination displayed resistance.Additional assays of 1306 current Chinese cultivars and breeding lines using markers flanking QYr SM155.1 and QYr SM155.2 indicated that the resistance haplotypes of the two QTL were present in respectively 1.45%and 14.16%of lines.Increasing resistance haplotype frequencies at these two loci using marker-assisted selection should benefit wheat production in China.展开更多
Highly efficient and stable polymer solar cells （PSCs） have been fabricated by adopting solution-derived hybrid poly（ethylene glycol）-titanium oxide （PEG-TiOx） nanocomposite films as a novel and universal cathod...Highly efficient and stable polymer solar cells （PSCs） have been fabricated by adopting solution-derived hybrid poly（ethylene glycol）-titanium oxide （PEG-TiOx） nanocomposite films as a novel and universal cathode buffer layer （CBL）, which can greatly improve device performance by reducing interface energy barriers and enhancing charge extraction/collection. The performance of inverted PSCs with varied bulk-heterojunctions （BHJs） based on this hybrid nanocomposite CBL was found to be much better than those of control devices with a pure TiOx CBL or without a CBL. An excellent power conversion efficiency up to 9.05% under AM 1.5G irradiation （100 mW-cm^-2） was demonstrated, which represents a record high value for inverted PSCs with TiOx-based interface materials.展开更多
基金National Natural Science Foundation of China,No.U23A2020National Science and Technology Basic Resource Investigation Program,No.2023FY100701。
文摘In the context of global warming,escalating water cycles have led to a surge in drought frequency and severity.Yet,multidecadal fluctuations in drought and their multifaceted influencing factors remain inadequately understood.This study examined the multidecadal changes in drought characteristics(frequency,duration,and severity)and their geographical focal points within China's north-south transitional zone,the Qinling-Daba Mountains(QDM),from 1960 to 2017 using the Standardized Precipitation Evapotranspiration Index(SPEI).In addition,a suite of eight scenarios,correlation analysis,and wavelet coherence were used to identify the meteorological and circulation factors that influenced drought characteristics.The results indicate the following:(1)From 1960 to 2017,the QDM experienced significant interdecadal variations in drought frequency,duration,and severity,the climate was relatively humid before the 1990s,but drought intensified thereafter.Specifically,the 1990s marked the period of the longest drought duration and greatest severity,while the years spanning 2010 to 2017 experienced the highest frequency of drought events.(2)Spatially,the Qinling Mountains,particularly the western Qinling Mountain,exhibited higher drought frequency,duration,and severity than the Daba Mountains.This disparity can be attributed to higher rates of temperature increase and precipitation decrease in the western Qinling Mountain.(3)Interdecadal variations in droughts in the QDM were directly influenced by the synergistic effects of interdecadal fluctuations in air temperature and precipitation.Circulation factors modulate temperature and precipitation through phase transitions,thereby affecting drought dynamics in the QDM.The Atlantic Multidecadal Oscillation emerges as the primary circulation factors influencing temperature changes,with a mid-1990s shift to a positive phase favoring warming.The East Asian Summer Monsoon and El Ni?o-Southern Oscillation are the main circulation factors affecting precipitation changes,with positive pha
基金support from the National Natural Science Foundation of China(U1605241)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-SLH032)。
文摘Recently,perovskite solar cells(PVSCs)based on CsPbI2Br have attracted increasing attention owing to their good balance between efficiency and stability.Solutionprocessed CsPbI2Br perovskites usually contain various defects which need passivation for PVSCs with high-performance as well as good stability.Since the degradation of perovskite films usually begins at the grain boundaries,here we report a facile defect passivation strategy by spin-coating a KF solution on the CsPbI2Br perovskite surface.The deposited KF salt mostly locates at the grain boundaries of the perovskite surface,resulting in PVSCs with improved stability.Both steady-state and time-resolved photoluminescence results suggest that the defects of perovskite were significantly passivated by KF treatment.Consequently,the best-performance PVSC based on CsPbI2Br with KF treatment shows an enhanced power conversion efficiency(PCE)of 15.01%with a larger open circuit voltage(VOC)of 1.26 V in comparison with the pristine CsPbI2Br-based counterpart which exhibits an inferior PCE of 14.14%with a VOC of 1.18 V.
基金supported by the National Natural Science Foundation of China(Nos.52130306,22075287)the Program of Youth Innovation Promotion Association CAs(No.2021299).
文摘Comprehensive Summary,The development of novel building blocks with sp3-hybridized-carbon-free conjugated skeletons is important to further advance and enrich nonfullerene acceptors(NFAs),but this remains a challenge due to the lack of strategies to effectively modulate the aggregation behavior of resulting NFAs.Herein,two novel nitrogen-bridged octacyclic ladder-type heteroarenes end-capped with thiophene rings(BTPS)or selenophene rings(BTPSe)are designed and synthesized as the donor cores for constructing NFAs(MQX-2 and MQX-4).It is found that replacing the sulfur atoms(MQX-2)at the outer positions of the heteroarene core with selenium atoms(MQX-4)can effectively modulate the molecular packing mode of the NFAs.The incorporation of selenium atoms induces stronger O···Se noncovalent interaction than O···S,thus promoting the formation of mixed H/J-type aggregates in MQX-4.Benefiting from more electron hopping channels,MQX-4 exhibits higher electron transport(more than 1-fold enhancement)and photovoltaic properties compared to MQX-2,which forms only H-type aggregates.
基金supported by the National Natural Science Foundation of China(nos.22101285,51873138,52130306,21734009,and 22075287)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)(no.QYZDB-SSW-SLH032)+2 种基金the China Postdoctoral Science Foundation(no.2021M703218)the Program of Youth Innovation Promotion Association CAS(no.2021000060)Beijing National Laboratory for Molecular Sciences(no.BNLMS201902).
文摘Asymmetric nonfullerene acceptors(NFAs)possess larger dipole moments and stronger intermolecular bonding energy than their symmetric counterparts thereby making them promising candidates for high-performance polymer solar cells(PSCs).Herein,we report twoefficient acceptor–donor–acceptor(A–D–A)type NFAs(M14 and M18)with asymmetric side chains that show enhanced intermolecular interactions compared with their corresponding counterparts(M17 and M19)based on symmetric side chains.Furthermore,M14 and M18 exhibit elevated lowest unoccupiedmolecular orbitals and smallerπ–πstacking distances in comparison with M17 and M19,respectively.In combination with the benchmark polymer donor of PM6,the PM6:M14 blend affords superior charge transport properties,and more importantly,an increased power conversion efficiency(PCE)of 15.49%in comparison with the M17-based counterpart(13.01%PCE).Similarly,the asymmetric M18-based blend also shows a higher PCE of 13.00%than the M19-based blend(11.55%).Through further interface engineering,the bestperforming M14-based device delivers an enhanced PCE of 16.46%,which represents a record value among all asymmetric A–D–A type NFAs.Our results provide new insights into the design of asymmetric NFAs with enhanced intermolecular interactions for highperformance PSCs.
基金supported by the National Natural Science Foundation of China (U1605241)the Key Research Program of Frontier Sciences, CAS (QYZDB-SSW-SLH032)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB20030300)
文摘Defect passivation is an important strategy to achieve perovskite solar cells(PVSCs) with enhanced power conversion efficiencies(PCEs) and improved stability because the trap states induced by defects in the interfaces and grain boundaries of perovskites are harmful to both large open circuit voltage and high photocurrent of devices. Here, zinc cations(Zn^2+) were used as a dopant to passivate defects of the CsPbI2Br perovskite leading to Zn^2+-doped CsPbI2Br film with fewer trap states, improved charge transportation, and enhanced light-harvesting ability. Thus, the best-performance PVSC based on CsPbI2 Br with the optimal Zn^2+doping shows a higher PCE of 12.16% with a larger open-circuit voltage(VOC) of 1.236 V, an improved shortcircuit current(JSC) of 15.61 mA cm^-2 in comparison with the control device based on the pure CsPbI2Br which exhibits a PCE of 10.21% with a VOCof 1.123 V, a JSCof 13.27 mA cm^-2. Time-resolved photoluminescence results show that the Zn^2+doping leads to perovskite film with extended photoluminescence lifetime which means a longer diffusion length and subsequently enhanced photocurrent and open circuit voltage. This work provides a simple strategy to boost the performance of PVSCs through Zn^2+doping.
基金National Natural Science Foundation of China,Grant/Award Numbers:52130306,22075287,22101285Program of Youth Innovation Promotion Association CAS,Grant/Award Number:2021299。
文摘Controlling the aggregation of small-molecule acceptors(SMAs)is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells(PSCs).However,reducing intermolecular aggregation of SMAs is usually accompanied by the disruption of compact molecular packing thereby leading to their decreased electron mobilities.Here,two novel M-series SMAs(MD1T and MD2T)based on ladder-type heterononacenes with neighboring side-chains separated by one or two thiophene rings are designed and synthesized.It is found that shortening the spacing of the neighboring side-chains of the SMAs can greatly alleviate the intermolecular aggregation and alter the molecular orientation from bimodal edge-on/face-on to predominant face-on while maintaining the compact molecular packing.As a result,a more favorable morphology with smaller domain sizes is formed for the MD1T-based blend films,which greatly improves the charge generation and charge transport for the corresponding PSCs.The best-performing MD1T-based device affords an efficiency of 12.43%,over seven times higher than that of the MD2T-based device.This work reveals the importance of the spacing between the neighboring side-chains in modulating the molecular aggregation and active layer morphology,and the obtained structure-performance relationships shall provide important guidance for designing highly efficient SMAs.
基金supported by the National Natural Science Foundation of China(Nos.52130306,22075287,22101285)the Program of Youth Innovation Promotion Association CAS(No.2021299).
文摘Optimal bulk-heterojunction(BHJ)morphology is crucial for efficient charge transport and good photovoltaic performance in organic solar cells(OSCs).Yet,the correlation between chemical structures of nonfullerene acceptors(NFAs)and molecular interaction in the BHJ blends remains opaque.Herein,we study three isomeric NFAs referred to as MQ1-x(x=β,y,or 8)that shared an asymmetric selenophene-fused heteroheptacene backbone end-capped by two monochlorinated end groups.Remarkably,miscibility between the polymer donor of PM6 and MQ1-x successively elevates as the chlorine atoms move fromβ-,to y-,to 8-position of terminals.Combined with the varied molecular crystallinity of these NFAs,diverse BHJ morphologies are observed in their blend films.As a result,the MQ1-8-based devices present the highest PCE of 12.08%owing to the efficient charge dissociation and transport induced by the compact molecular packing and optimal BHJ morphology.Our investigation provides a new insight in the material design that has a good balance in molecular packing and film morphology for high-performance OSCs.
基金financially the National Natural Science Foundation of China(31871611 and31971890)the National Science Foundation for Young Scientistsin China(31901494 and 31901869)+1 种基金International Cooperation and Exchange of the National Natural Science Foundation of China(31961143019)the Integrated Extension Project of Agricultural Science and Technology Innovation in Shaanxi Province(NYKJ-2021-YL(XN)15)。
文摘The development and deployment of diverse resistance sources in new wheat cultivars underpin the durable control of stripe rust.In the present study,two loci for adult plant resistance(APR),QYr SM155.1 and QYr SM155.2,were identified in the Chinese wheat breeding line Shaanmai 155.QYr SM155.1 was mapped to a 3.0-c M interval between the single-nucleotide polymorphism(SNP)markers AX-109583610 and AX-110907562 on chromosome arm 2 BL.QYr SM155.2 was mapped to a 2.1-c M interval flanked by the SNP markers AX-110378556 and AX-86173526 on chromosome arm 7 AS.A genome-wide association study was used to identify markers associated with APR in a panel of 411 spring wheat lines.Thirteen and 11 SNPs were significantly associated with QYr SM155.1 and QYr SM155.2,respectively,corresponding to physical intervals of 653.75–655.52 Mb on 2 BL and 81.63–83.93 Mb on7 AS.To characterize the haplotype variation and the distribution of these QTL,haplotype analysis was performed based on these SNPs in an independent panel of 1101 worldwide wheat accessions.Three major haplotypes(2 B_h1,2 B_h2,and 2 B_h3)for QYr SM155.1 and four major haplotypes(7 A_h1,7 A_h2,7 A_h3,and 7 A_h4)for QYr SM155.2 were identified.Accessions individually harboring QYr SM155.1_h1 and QYr SM155.2_h1 haplotypes and their combination displayed resistance.Additional assays of 1306 current Chinese cultivars and breeding lines using markers flanking QYr SM155.1 and QYr SM155.2 indicated that the resistance haplotypes of the two QTL were present in respectively 1.45%and 14.16%of lines.Increasing resistance haplotype frequencies at these two loci using marker-assisted selection should benefit wheat production in China.
文摘Highly efficient and stable polymer solar cells （PSCs） have been fabricated by adopting solution-derived hybrid poly（ethylene glycol）-titanium oxide （PEG-TiOx） nanocomposite films as a novel and universal cathode buffer layer （CBL）, which can greatly improve device performance by reducing interface energy barriers and enhancing charge extraction/collection. The performance of inverted PSCs with varied bulk-heterojunctions （BHJs） based on this hybrid nanocomposite CBL was found to be much better than those of control devices with a pure TiOx CBL or without a CBL. An excellent power conversion efficiency up to 9.05% under AM 1.5G irradiation （100 mW-cm^-2） was demonstrated, which represents a record high value for inverted PSCs with TiOx-based interface materials.
