Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness,high element abundance,and low cost.Here,we developed a strategy of one-step ga...Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness,high element abundance,and low cost.Here,we developed a strategy of one-step gas-solid-phase diffusioninduced reaction to fabricate a series of bandgap-tunable Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI bilayer films due to the atomic diffusion effect for the first time.By designing and regulating the sputtered Cu/Ag/Bi metal film thickness,the bandgap of Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI could be reduced from 2.06 to 1.78 eV.Solar cells with the structure of FTO/TiO_(2)/Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI/carbon were constructed,yielding a champion power conversion efficiency of 2.76%,which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure.The current work provides a practical path for developing the next generation of efficient,stable,and environmentally friendly photovoltaic materials.展开更多
We investigated the structural and optical properties of amorphous-SiGe thin films synthesized via a low-cost, high-growth rate deposition method. Films were formed by e-beam evaporation of mixed pellets of Si and Ge....We investigated the structural and optical properties of amorphous-SiGe thin films synthesized via a low-cost, high-growth rate deposition method. Films were formed by e-beam evaporation of mixed pellets of Si and Ge. Film composition was varied by changing the weight ratio of Si and Ge pellets mixture. Films were amorphous with a composition uniform. Ge-rich films are in tensile stress, while Si-rich films are in compressive stress. As the Ge fraction increases (from 22 at.% to 94 at.%), the optical bandgap decreases (from 1.7 eV to 0.9 eV) and the photosensitivity of the films extends into IR band of solar spectrum. By changing the weighted ratio of the evaporation source mixture, the bandgap and optical sensitivity of a-SiGe films can be easily tuned. Our studies prove that a-SiGe films are a tunable absorber. This can be used for photo-detector, photovoltaic and microelectronic applications to extend the spectral response.展开更多
ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique. XRD analysis indicates that the crystal quality of the ZnO：Cu film can be enhanced by a moderate level ...ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique. XRD analysis indicates that the crystal quality of the ZnO：Cu film can be enhanced by a moderate level of Cu-doping in the sputtering process. The results of XPS spectra of zinc, oxygen, and copper elements show that Cu-doping has an evident and complicated effect on the chemical state of oxygen, but little effect on those of zinc and copper. Interestingly, further investigation of the optical properties of ZnO：Cu samples shows that the transmittance spectra exhibit both red shift and blue shift with the increase of Cu doping, in contrast to the simple monotonic behavior of the Burstein–Moss effect. Analysis reveals that this is due to the competition between oxygen vacancies and intrinsic and surface states of oxygen in the sample. Our result may suggest an effective way of tuning the bandgap of ZnO samples.展开更多
According to band folding analyses, the graphene superlattices can be differed by whether the Dirac points are folded to Γ point or not. In previous studies, the inversion symmetry preserved defects open bandgap in t...According to band folding analyses, the graphene superlattices can be differed by whether the Dirac points are folded to Γ point or not. In previous studies, the inversion symmetry preserved defects open bandgap in the former superlattices while they cannot in the latter ones. In this paper, by using density functional theory with generalized gradient approximation, we have carefully studied the electronic properties of the latter graphene superlattices, in which the defects would induce π-band splitting to get the π_a1–π_a2 and π_z1–π_z2 band sets. Based on our detailed studies, such splitting could be attributed to the geometrically induced bond-symmetry breaking. In addition, these band sets could be shifted toward each other by the methodology of strain engineering. A bandgap would be opened once the band sets start to overlap. Then,its gap width could be continuously enlarged by enhancing strain until reaching the maximum value determined by the defect density. These studies contribute to the bandstructure engineering of graphene-based nanomaterials, which would be interesting to call for further investigations on both theory and experiment.展开更多
Halide perovskites have become a hot topic in materials research due to their potential applications in a variety of fields,from optoelectronic and thermoelectric devices to solar cells.Doping of halide perovskites ca...Halide perovskites have become a hot topic in materials research due to their potential applications in a variety of fields,from optoelectronic and thermoelectric devices to solar cells.Doping of halide perovskites can be achieved by introducing different types of dopants,such as metal cations,anions,and organic molecules,leading to increased stability and improved optoelectronic properties.Moreover,doping can introduce new functionalities,such as increased spin lifetime and thermal stability.These features make doped halide perovskites a highly promising candidate for optoelectronic applications.In this mini-review,we highlight the latest advances in ion-doped halide perovskites and their immense potential for various applications.展开更多
基金supported by National Natural Science Foundation of China(Grant No.52072327,62074052,61874159)Zhongyuan Thousand Talents(Zhongyuan Scholars)Program of Henan Province(202101510004)+6 种基金Higher Education and Teaching Reformation Project(2014SJGLX064)Academic Degrees&Graduate Education Reform Project of Henan Province(2021SJGLX060Y)Key research and development projects of Universities in Henan Province(20A140026)the Scientific Research Innovation Team of Xuchang University(2022CXTD008)Science and Technology Project of Henan Province(222102230009).L.Ding thanks the National Key Research and Development Program of China(2022YFB3803300)the open research fund of Songshan Lake Materials Laboratory(2021SLABFK02)the National Natural Science Foundation of China(21961160720).
文摘Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness,high element abundance,and low cost.Here,we developed a strategy of one-step gas-solid-phase diffusioninduced reaction to fabricate a series of bandgap-tunable Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI bilayer films due to the atomic diffusion effect for the first time.By designing and regulating the sputtered Cu/Ag/Bi metal film thickness,the bandgap of Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI could be reduced from 2.06 to 1.78 eV.Solar cells with the structure of FTO/TiO_(2)/Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI/carbon were constructed,yielding a champion power conversion efficiency of 2.76%,which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure.The current work provides a practical path for developing the next generation of efficient,stable,and environmentally friendly photovoltaic materials.
文摘We investigated the structural and optical properties of amorphous-SiGe thin films synthesized via a low-cost, high-growth rate deposition method. Films were formed by e-beam evaporation of mixed pellets of Si and Ge. Film composition was varied by changing the weight ratio of Si and Ge pellets mixture. Films were amorphous with a composition uniform. Ge-rich films are in tensile stress, while Si-rich films are in compressive stress. As the Ge fraction increases (from 22 at.% to 94 at.%), the optical bandgap decreases (from 1.7 eV to 0.9 eV) and the photosensitivity of the films extends into IR band of solar spectrum. By changing the weighted ratio of the evaporation source mixture, the bandgap and optical sensitivity of a-SiGe films can be easily tuned. Our studies prove that a-SiGe films are a tunable absorber. This can be used for photo-detector, photovoltaic and microelectronic applications to extend the spectral response.
基金Project supported by the Natural Science Foundation of Gansu Province, China (Grant No. 0803RJZA008)the Fundamental Research Funds for the Central Universities, China (Grant No. zyz2012057)+1 种基金the National Natural Science Foundation of China (Grant No. 11004141)the Program for New Century Excellent Talents in University, China (Grant No. 11-0351)
文摘ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique. XRD analysis indicates that the crystal quality of the ZnO：Cu film can be enhanced by a moderate level of Cu-doping in the sputtering process. The results of XPS spectra of zinc, oxygen, and copper elements show that Cu-doping has an evident and complicated effect on the chemical state of oxygen, but little effect on those of zinc and copper. Interestingly, further investigation of the optical properties of ZnO：Cu samples shows that the transmittance spectra exhibit both red shift and blue shift with the increase of Cu doping, in contrast to the simple monotonic behavior of the Burstein–Moss effect. Analysis reveals that this is due to the competition between oxygen vacancies and intrinsic and surface states of oxygen in the sample. Our result may suggest an effective way of tuning the bandgap of ZnO samples.
基金Project jointly supported by the Natural Science Foundation of Shandong Province(Grant NO.TSHW20101004)the National Natural Science Foundation of China(Grant Nos.11374128 and 11674129)
文摘According to band folding analyses, the graphene superlattices can be differed by whether the Dirac points are folded to Γ point or not. In previous studies, the inversion symmetry preserved defects open bandgap in the former superlattices while they cannot in the latter ones. In this paper, by using density functional theory with generalized gradient approximation, we have carefully studied the electronic properties of the latter graphene superlattices, in which the defects would induce π-band splitting to get the π_a1–π_a2 and π_z1–π_z2 band sets. Based on our detailed studies, such splitting could be attributed to the geometrically induced bond-symmetry breaking. In addition, these band sets could be shifted toward each other by the methodology of strain engineering. A bandgap would be opened once the band sets start to overlap. Then,its gap width could be continuously enlarged by enhancing strain until reaching the maximum value determined by the defect density. These studies contribute to the bandstructure engineering of graphene-based nanomaterials, which would be interesting to call for further investigations on both theory and experiment.
基金supported by the Singapore Quantum engineering program(grant no.RF2021-QEP2-03-P10)the National Research Foundation,the Prime Minister’s Office,and the government of Singapore under its Competitive Research Programme(award no.NRF-CRP23-2019-0002)its NRF Investigatorship Programme(award no.NRF-NRFI05-2019-0003).
文摘Halide perovskites have become a hot topic in materials research due to their potential applications in a variety of fields,from optoelectronic and thermoelectric devices to solar cells.Doping of halide perovskites can be achieved by introducing different types of dopants,such as metal cations,anions,and organic molecules,leading to increased stability and improved optoelectronic properties.Moreover,doping can introduce new functionalities,such as increased spin lifetime and thermal stability.These features make doped halide perovskites a highly promising candidate for optoelectronic applications.In this mini-review,we highlight the latest advances in ion-doped halide perovskites and their immense potential for various applications.
