To further promote the achievable average secrecy rate for UAV-ground communications, a UAV-aided mobile jamming strategy was proposed in this paper. Specifically, an additional cooperative UAV is employed as a mobile...To further promote the achievable average secrecy rate for UAV-ground communications, a UAV-aided mobile jamming strategy was proposed in this paper. Specifically, an additional cooperative UAV is employed as a mobile jammer to transmit the jamming signal to help keep the source UAV closer to the ground destination, thus establishing more favorable legitimate link and enhancing the secrecy performance. We aimed to maximize the achievable secrecy rate by jointly optimizing the trajectories and transmit power of both source UAV and jammer UAV. To solve the considered non-convex optimization problem, we presented a block coordinate descent based iterative algorithm to address a sequence of approximated convex problems for the optimized parameter block by block to find a local optimal solution. Numerical results verify that the proposed algorithm can achieve significant secrecy rate gain compared to all the benchmark schemes.展开更多
Perovskite solar cells(PSCs) have demonstrated excellent photovoltaic performance which currently rival the long-standing silicon solar cells’ efficiency. However, the relatively poor device operational stability of ...Perovskite solar cells(PSCs) have demonstrated excellent photovoltaic performance which currently rival the long-standing silicon solar cells’ efficiency. However, the relatively poor device operational stability of PSCs still limits their future commercialization. Binary sulfide is a category of materials with promising optoelectrical properties, which shows the potential to improve both the efficiency and stability of PSCs.Here we demonstrate that the inorganic tin monosulfide(Sn S) can be an efficient dopant in 2,2’,7,7’-tet rakis(N,N-di-p-methoxy-phenylamine)-9,9’-spirobifluorene(spiro-OMe TAD) to form a composite hole transport layer(HTL) for PSCs. Sn S nanoparticles(NPs) synthesized through a simple chemical precipitation method exhibit good crystallization and suitable band matching with the perovskites. The introduction of Sn S NPs in Spiro-OMTAD HTLs enhanced charge extraction, reduced trap state density, and shallowed trap state energy level of the devices based on the composite HTLs. Therefore, the resulting solar cells employing Sn S-doped spiro-OMe TAD HTLs delivered an improved stabilized power output efficiency of 21.75% as well as enhanced long-term stability and operational stability. Our results provide a simple method to modify the conventional spiro-OMe TAD and obtain PSCs with both high efficiency and good stability.展开更多
As a traditional n-type semiconductor, TiO_(2)has good UV absorption ability and stable physical and chemical properties. However, its wide band gap and low oxygen evolution reaction(OER) activity limit its applicatio...As a traditional n-type semiconductor, TiO_(2)has good UV absorption ability and stable physical and chemical properties. However, its wide band gap and low oxygen evolution reaction(OER) activity limit its application in the field of photoelectrochemical(PEC) water splitting. In this work, a type-Ⅱ TiO2/CuNi2S4heterojunction photoanode is successfully constructed, which expanded the light absorption range to visible and enhanced the OER activity. Firstly, TiO2nanotubes(NTs) thin films are prepared on Ti substrates by two-step anodization, and then the bi-functional electrocatalytic material CuNi2S4is grown on TiO2NTs in the shape of nanosheets(NSs) in situ by solvothermal method. As a bi-functional electrocatalytic material, CuNi2S4has good visible light absorption property as well as OER catalytic activity. Compared with TiO_(2), the IPCE value of TiO_(2)/CuNi_(2)S_(4)is 2.59% at 635 nm, and that of TiO2is a mere 0.002%.The separation efficiency and injection efficiency increase from 2.49% and 31.52% to 3.61% and 87.77%, respectively. At 1.23 V vs. RHE, the maximum photocurrent density is 0.26 m A/cm^(2), which is 2.6 times than that of TiO2(0.11 m A/cm^(2)),and can be maintained at 0.25 m A/cm^(2)for at least 2 h under light illumination. Moreover, a hydrogen production rate of 4.21 μmol·cm^(-2)·h^(-1)is achieved within 2 h. This work provides a new idea for the application of TiO_(2)in the field of PEC water splitting and the construction of efficient and stable photoelectronic devices.展开更多
基金partly supported by National Natural Science Foundation of China (No. 41504026, 61362009)Natural Science Foundation of Jiangxi (No.20152ACB21003)Foundation for Distinguished Young Talents Training Programme of Jiangxi (No.20171BCB23006)
文摘To further promote the achievable average secrecy rate for UAV-ground communications, a UAV-aided mobile jamming strategy was proposed in this paper. Specifically, an additional cooperative UAV is employed as a mobile jammer to transmit the jamming signal to help keep the source UAV closer to the ground destination, thus establishing more favorable legitimate link and enhancing the secrecy performance. We aimed to maximize the achievable secrecy rate by jointly optimizing the trajectories and transmit power of both source UAV and jammer UAV. To solve the considered non-convex optimization problem, we presented a block coordinate descent based iterative algorithm to address a sequence of approximated convex problems for the optimized parameter block by block to find a local optimal solution. Numerical results verify that the proposed algorithm can achieve significant secrecy rate gain compared to all the benchmark schemes.
基金supported by the Special Funds for the Development of Strategic Emerging Industries in Shenzhen(JCYJ20190808152609307)Shenzhen Science and Technology Research Program (JCYJ20180507182057026)the Natural Science Foundation of Hubei Province,China (2019AAA020)。
文摘Perovskite solar cells(PSCs) have demonstrated excellent photovoltaic performance which currently rival the long-standing silicon solar cells’ efficiency. However, the relatively poor device operational stability of PSCs still limits their future commercialization. Binary sulfide is a category of materials with promising optoelectrical properties, which shows the potential to improve both the efficiency and stability of PSCs.Here we demonstrate that the inorganic tin monosulfide(Sn S) can be an efficient dopant in 2,2’,7,7’-tet rakis(N,N-di-p-methoxy-phenylamine)-9,9’-spirobifluorene(spiro-OMe TAD) to form a composite hole transport layer(HTL) for PSCs. Sn S nanoparticles(NPs) synthesized through a simple chemical precipitation method exhibit good crystallization and suitable band matching with the perovskites. The introduction of Sn S NPs in Spiro-OMTAD HTLs enhanced charge extraction, reduced trap state density, and shallowed trap state energy level of the devices based on the composite HTLs. Therefore, the resulting solar cells employing Sn S-doped spiro-OMe TAD HTLs delivered an improved stabilized power output efficiency of 21.75% as well as enhanced long-term stability and operational stability. Our results provide a simple method to modify the conventional spiro-OMe TAD and obtain PSCs with both high efficiency and good stability.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11974276 and 11804274)the Natural Science Foundation of Shaanxi Province of China (Grant No. 2023-JC-YB-139)+1 种基金the Open Research Fund of State Key Laboratory of Transient Optics and Photonicsthe Chinese Academy of Sciences (Grant No. SKLST202211)。
文摘As a traditional n-type semiconductor, TiO_(2)has good UV absorption ability and stable physical and chemical properties. However, its wide band gap and low oxygen evolution reaction(OER) activity limit its application in the field of photoelectrochemical(PEC) water splitting. In this work, a type-Ⅱ TiO2/CuNi2S4heterojunction photoanode is successfully constructed, which expanded the light absorption range to visible and enhanced the OER activity. Firstly, TiO2nanotubes(NTs) thin films are prepared on Ti substrates by two-step anodization, and then the bi-functional electrocatalytic material CuNi2S4is grown on TiO2NTs in the shape of nanosheets(NSs) in situ by solvothermal method. As a bi-functional electrocatalytic material, CuNi2S4has good visible light absorption property as well as OER catalytic activity. Compared with TiO_(2), the IPCE value of TiO_(2)/CuNi_(2)S_(4)is 2.59% at 635 nm, and that of TiO2is a mere 0.002%.The separation efficiency and injection efficiency increase from 2.49% and 31.52% to 3.61% and 87.77%, respectively. At 1.23 V vs. RHE, the maximum photocurrent density is 0.26 m A/cm^(2), which is 2.6 times than that of TiO2(0.11 m A/cm^(2)),and can be maintained at 0.25 m A/cm^(2)for at least 2 h under light illumination. Moreover, a hydrogen production rate of 4.21 μmol·cm^(-2)·h^(-1)is achieved within 2 h. This work provides a new idea for the application of TiO_(2)in the field of PEC water splitting and the construction of efficient and stable photoelectronic devices.
