Graphitic carbon nitride(g-C_(3)N_(4))is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applicat...Graphitic carbon nitride(g-C_(3)N_(4))is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applications.Currently,synthesizing highly crystalline g-C_(3)N_(4) with sufficient surface activities still remains challenging.Herein,different from using alkali molten salts which is commonly reported,we propose an approach for synthesis of highly crystalline g-C_(3)N_(4) with FeCl3/KCl rock/molten mixed salts.The rock salt can serve as the structure-directing template while molten salt provides the required liquid medium for re-condensation.Intriguingly,the synthesized photocatalyst showed further enhanced crystallinity and improved surface area along with high p/p*excitation compared with crystalline C_(3)N_(4) prepared from conventional molten-salt methods.These catalytically advantageous features lead to its superior photocatalytic and piezocatalytic activities with a high reactivity for overall water splitting that is not commonly reported for C_(3)N_(4).This work provides an effective strategy for structural optimization of organic semiconductor based materials and may inspire new ideas for the design of advanced photocatalysts.展开更多
Carbazole moiety-based 2PACz([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)self-assembled monolayers(SAMs)are excellent hole-selective contact(HSC)materials with abilities to excel the charge-transferdynamics of perovski...Carbazole moiety-based 2PACz([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)self-assembled monolayers(SAMs)are excellent hole-selective contact(HSC)materials with abilities to excel the charge-transferdynamics of perovskite solar cells(PSCs).Herein,we report a facile but powerful method to functionalize the surface of 2PACz-SAM,by which reproducible,highly stable,high-efficiency wide-bandgap PSCs can be obtained.The 2PACz surface treatment with various donor number solvents improves assembly of 2PACz-SAM and leave residual surface-bound solvent molecules on 2PACz-SAM,which increases perovskite grain size,retards halide segregation,and accelerates hole extraction.The surface functionalization achieves a high power conversion efficiency(PCE)of 17.62%for a single-junction wide-bandgap(~1.77 e V)PSC.We also demonstrate a monolithic all-perovskite tandem solar cell using surfaceengineered HSC,showing high PCE of 24.66%with large open-circuit voltage of 2.008 V and high fillfactor of 81.45%.Our results suggest this simple approach can further improve the tandem device,when coupled with a high-performance narrow-bandgap sub-cell.展开更多
A supersonic turbulent flowfield involving the pseudo-shock waves in an isolator of a supersonic combustion ramjet is computed using two different LES codes which are a high-order upwind finite volume scheme, and a si...A supersonic turbulent flowfield involving the pseudo-shock waves in an isolator of a supersonic combustion ramjet is computed using two different LES codes which are a high-order upwind finite volume scheme, and a sixth order compact differencing scheme utilizing the localized artificial diffusivity method for stabilizing shock waves and employing a wall model to enable the use of coarse mesh. In the validation study where a supersonic turbulent boundary layer flow over a flat plate is examined, both LES codes are well validated using velocity profile in the boundary layer given by the hot-wire anemometry and normal stress given by the laser Doppler anemometry. In particular, the sixth order compact differencing scheme gives closer agreements with these experimental data. Then, the validated LES codes are applied to solve the Mach number 2.5 supersonic turbulent flowfield involving the pseudo-shock waves. It is shown that typical features of unsteady flowfield of the pseudo-shock waves are well obtained by both schemes. Again, it is indicated that the sixth order compact differencing scheme gives closer agreements with the existing velocity data obtained by particle image velocimetry and pressure fluctuation data on the wall surface. Besides, the computational cost of the compact differencing scheme is found to be 1/7 of that for the upwind finite volume scheme, even though a wall model is solved at each grid point on the wall surface. Therefore, the obtained results in the present study allow recommending the sixth order compact differencing scheme with a wall model for simulating supersonic turbulent flowfield in an isolator involving the pseudo-shock waves.展开更多
Blue photodetectors(PDs)are attracting great attention for various applications.Commercial blue PDs based on inorganic GaP or InGaN absorbers are limited by their expensive,complex,and high-temperature fabrication tec...Blue photodetectors(PDs)are attracting great attention for various applications.Commercial blue PDs based on inorganic GaP or InGaN absorbers are limited by their expensive,complex,and high-temperature fabrication techniques.Organic absorber-based blue PDs still have much lower photode-tecting properties than inorganic blue PDs.In this study,a high-performance self-powered blue PD is developed using methylammonium lead halide(MAPbX_(3);X=I,Br,and Cl)perovskites based on the eco-nomic and facile solution process at low temperatures.Optimal composition is obtained through halide-composition engineering.Our best-performing device exhibits an average external quantum efficiency and an average detectivity of 42.7%and 8.65×10^(11) Jones,respectively,within the blue region.The peak responsivity of the proposed PD is 0.174 A W^(−1) at 455 nm,which is comparable to that of commercial gallium phosphide blue PD(0.180 A W^(−1) at 470 nm).Moreover,the proposed device exhibits excellent environmental stability under ambient air conditions.These findings will act as a basis for next-generation image sensor technologies,such as vertically stacked red/green/blue PDs.展开更多
Mixed tin-ead perovskites suffer from structural instability and rapid tin oxidation;thus,the investigation of their optimal composition ranges is important to address these inherent weaknesses.The critical role of tr...Mixed tin-ead perovskites suffer from structural instability and rapid tin oxidation;thus,the investigation of their optimal composition ranges is important to address these inherent weaknesses.The critical role of triple cations in mixed Sn–Pb iodides is studied by performing a wide range of compositional screenings over mechanochemically synthesized bulk and solution-processed thin films.A ternary phase map of FA(Sn_(0.6)Pb_(0.4))I_(3),MA(Sn_(0.6)Pb_(0.4))I_(3),and Cs(Sn_(0.6)Pb_(0.4))I_(3)is formed,and a promising composition window of(FA_(0.6-x)MA_(0.4)Cs_(x))Sn_(0.6)Pb_(0.4)I_(3)(0≤x≤0.1)is demonstrated through phase,photoluminescence,and stability evaluations.Solar cell performance and chemical stability across the targeted compositional space are investigated,and FA_(0.55)MA_(0.4)Cs_(0.05)Sn_(0.6)Pb_(0.4)I_(3)with strain-relaxed lattices,reduced defect densities,and improved oxidation stability is demonstrated.The inverted perovskite solar cells with the optimal composition demonstrate a power conversion efficiency of over 22%with an open-circuit voltage of 0.867 V,which corresponds to voltage loss of 0.363 V,promising for the development of narrow-bandgap perovskite solar cells.展开更多
作为过渡金属硫化物的代表, SnS因其优异的理论容量和独特的层状结构被认为是理想的钠离子电池负极材料.然而较差的导电性以及巨大的体积膨胀严重阻碍了SnS作为钠离子电池负极材料的实际应用,如何实现长循环寿命及高可逆容量是发展其作...作为过渡金属硫化物的代表, SnS因其优异的理论容量和独特的层状结构被认为是理想的钠离子电池负极材料.然而较差的导电性以及巨大的体积膨胀严重阻碍了SnS作为钠离子电池负极材料的实际应用,如何实现长循环寿命及高可逆容量是发展其作为高性能负极材料的巨大挑战.基于此,本文提出利用具有螯合作用的植酸作为磷源,并将PO_(4)^(3-)-引入SnS层间的结构修饰思路.研究发现不同于常规掺杂手段,以Sn±O±P共价键形式存在的PO_(4)^(3-)作为多向导电柱能够有效抑制SnS的结构塌陷并扩大层间间距,从而实现高效Na~+存储.密度泛函理论计算结果表明PO_(4)^(3-)的引入导致SnS内部电荷分布发生变化并产生内建电场,有效促进了Na^(+)的吸附.因此,所制备的PO_(4)-SnS/NG复合负极材料呈现出优异的超长循环寿命;在5 A g^(-1)下10,000次循环后,材料仍表现出优异的稳定性,每次容量衰减仅为0.0028%.该工作为制备高性能金属硫化物电极材料提供了新思路.展开更多
基金supported by the National Natural Science Foundation of China(51902045,51904059)Fundamental Research Funds for the Central Universities(N2002005,N2125004,N2225038,N2225044)+2 种基金Applied Basic Research Program of Liaoning(2022JH2/101300200)Young Elite Scientist Sponsorship Program by CAST(YESS)2019-2021QNRCNational Research Foundation of Korea(NRF)grant funded by the Korean government(Ministry of Science,ICT&Future Planning)(NRF-2020R1F1A1075601 and NRF-2021R1A4A2001658).
文摘Graphitic carbon nitride(g-C_(3)N_(4))is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applications.Currently,synthesizing highly crystalline g-C_(3)N_(4) with sufficient surface activities still remains challenging.Herein,different from using alkali molten salts which is commonly reported,we propose an approach for synthesis of highly crystalline g-C_(3)N_(4) with FeCl3/KCl rock/molten mixed salts.The rock salt can serve as the structure-directing template while molten salt provides the required liquid medium for re-condensation.Intriguingly,the synthesized photocatalyst showed further enhanced crystallinity and improved surface area along with high p/p*excitation compared with crystalline C_(3)N_(4) prepared from conventional molten-salt methods.These catalytically advantageous features lead to its superior photocatalytic and piezocatalytic activities with a high reactivity for overall water splitting that is not commonly reported for C_(3)N_(4).This work provides an effective strategy for structural optimization of organic semiconductor based materials and may inspire new ideas for the design of advanced photocatalysts.
基金supported by the National Research Foundation of Korea (NRF)the Ministry of Science,ICT (2022M3J1A1085285,2019R1A2C1084010,and 2022R1A2C2006532)the Korea Electric Power Corporation (R20XO02-1)。
文摘Carbazole moiety-based 2PACz([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)self-assembled monolayers(SAMs)are excellent hole-selective contact(HSC)materials with abilities to excel the charge-transferdynamics of perovskite solar cells(PSCs).Herein,we report a facile but powerful method to functionalize the surface of 2PACz-SAM,by which reproducible,highly stable,high-efficiency wide-bandgap PSCs can be obtained.The 2PACz surface treatment with various donor number solvents improves assembly of 2PACz-SAM and leave residual surface-bound solvent molecules on 2PACz-SAM,which increases perovskite grain size,retards halide segregation,and accelerates hole extraction.The surface functionalization achieves a high power conversion efficiency(PCE)of 17.62%for a single-junction wide-bandgap(~1.77 e V)PSC.We also demonstrate a monolithic all-perovskite tandem solar cell using surfaceengineered HSC,showing high PCE of 24.66%with large open-circuit voltage of 2.008 V and high fillfactor of 81.45%.Our results suggest this simple approach can further improve the tandem device,when coupled with a high-performance narrow-bandgap sub-cell.
文摘A supersonic turbulent flowfield involving the pseudo-shock waves in an isolator of a supersonic combustion ramjet is computed using two different LES codes which are a high-order upwind finite volume scheme, and a sixth order compact differencing scheme utilizing the localized artificial diffusivity method for stabilizing shock waves and employing a wall model to enable the use of coarse mesh. In the validation study where a supersonic turbulent boundary layer flow over a flat plate is examined, both LES codes are well validated using velocity profile in the boundary layer given by the hot-wire anemometry and normal stress given by the laser Doppler anemometry. In particular, the sixth order compact differencing scheme gives closer agreements with these experimental data. Then, the validated LES codes are applied to solve the Mach number 2.5 supersonic turbulent flowfield involving the pseudo-shock waves. It is shown that typical features of unsteady flowfield of the pseudo-shock waves are well obtained by both schemes. Again, it is indicated that the sixth order compact differencing scheme gives closer agreements with the existing velocity data obtained by particle image velocimetry and pressure fluctuation data on the wall surface. Besides, the computational cost of the compact differencing scheme is found to be 1/7 of that for the upwind finite volume scheme, even though a wall model is solved at each grid point on the wall surface. Therefore, the obtained results in the present study allow recommending the sixth order compact differencing scheme with a wall model for simulating supersonic turbulent flowfield in an isolator involving the pseudo-shock waves.
基金This work was financially supported by the National Re-search Foundation of Korea(NRF)funded by the Ministry of Science,ICT(Nos.NRF-2019M3D1A2104108,2019R1A2C1084010,2020R1A4A2002161,and 2020R1A6A3A13073172)。
文摘Blue photodetectors(PDs)are attracting great attention for various applications.Commercial blue PDs based on inorganic GaP or InGaN absorbers are limited by their expensive,complex,and high-temperature fabrication techniques.Organic absorber-based blue PDs still have much lower photode-tecting properties than inorganic blue PDs.In this study,a high-performance self-powered blue PD is developed using methylammonium lead halide(MAPbX_(3);X=I,Br,and Cl)perovskites based on the eco-nomic and facile solution process at low temperatures.Optimal composition is obtained through halide-composition engineering.Our best-performing device exhibits an average external quantum efficiency and an average detectivity of 42.7%and 8.65×10^(11) Jones,respectively,within the blue region.The peak responsivity of the proposed PD is 0.174 A W^(−1) at 455 nm,which is comparable to that of commercial gallium phosphide blue PD(0.180 A W^(−1) at 470 nm).Moreover,the proposed device exhibits excellent environmental stability under ambient air conditions.These findings will act as a basis for next-generation image sensor technologies,such as vertically stacked red/green/blue PDs.
基金supported by the Korea Electric Power Corporation(Grant number:R20XO02-1)the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT(NRF-2019R1A2C1084010).
文摘Mixed tin-ead perovskites suffer from structural instability and rapid tin oxidation;thus,the investigation of their optimal composition ranges is important to address these inherent weaknesses.The critical role of triple cations in mixed Sn–Pb iodides is studied by performing a wide range of compositional screenings over mechanochemically synthesized bulk and solution-processed thin films.A ternary phase map of FA(Sn_(0.6)Pb_(0.4))I_(3),MA(Sn_(0.6)Pb_(0.4))I_(3),and Cs(Sn_(0.6)Pb_(0.4))I_(3)is formed,and a promising composition window of(FA_(0.6-x)MA_(0.4)Cs_(x))Sn_(0.6)Pb_(0.4)I_(3)(0≤x≤0.1)is demonstrated through phase,photoluminescence,and stability evaluations.Solar cell performance and chemical stability across the targeted compositional space are investigated,and FA_(0.55)MA_(0.4)Cs_(0.05)Sn_(0.6)Pb_(0.4)I_(3)with strain-relaxed lattices,reduced defect densities,and improved oxidation stability is demonstrated.The inverted perovskite solar cells with the optimal composition demonstrate a power conversion efficiency of over 22%with an open-circuit voltage of 0.867 V,which corresponds to voltage loss of 0.363 V,promising for the development of narrow-bandgap perovskite solar cells.
基金supported by the National Natural Science Foundation of China(51904059)Fundamental Research Funds for the Central Universities(N2002005,N2125004,and N2225044)+1 种基金Applied Basic Research Program of Liaoning(2022JH2/101300200)。
文摘作为过渡金属硫化物的代表, SnS因其优异的理论容量和独特的层状结构被认为是理想的钠离子电池负极材料.然而较差的导电性以及巨大的体积膨胀严重阻碍了SnS作为钠离子电池负极材料的实际应用,如何实现长循环寿命及高可逆容量是发展其作为高性能负极材料的巨大挑战.基于此,本文提出利用具有螯合作用的植酸作为磷源,并将PO_(4)^(3-)-引入SnS层间的结构修饰思路.研究发现不同于常规掺杂手段,以Sn±O±P共价键形式存在的PO_(4)^(3-)作为多向导电柱能够有效抑制SnS的结构塌陷并扩大层间间距,从而实现高效Na~+存储.密度泛函理论计算结果表明PO_(4)^(3-)的引入导致SnS内部电荷分布发生变化并产生内建电场,有效促进了Na^(+)的吸附.因此,所制备的PO_(4)-SnS/NG复合负极材料呈现出优异的超长循环寿命;在5 A g^(-1)下10,000次循环后,材料仍表现出优异的稳定性,每次容量衰减仅为0.0028%.该工作为制备高性能金属硫化物电极材料提供了新思路.
