We report the performances of a chalcopyrite Cu(In, Ga)Se<sub>2 </sub>CIGS-based thin-film solar cell with a newly employed high conductive n-Si layer. The data analysis was performed with the help of the ...We report the performances of a chalcopyrite Cu(In, Ga)Se<sub>2 </sub>CIGS-based thin-film solar cell with a newly employed high conductive n-Si layer. The data analysis was performed with the help of the 1D-Solar Cell Capacitance Simulator (1D-SCAPS) software program. The new device structure is based on the CIGS layer as the absorber layer, n-Si as the high conductive layer, i-In<sub>2</sub>S<sub>3</sub>, and i-ZnO as the buffer and window layers, respectively. The optimum CIGS bandgap was determined first and used to simulate and analyze the cell performance throughout the experiment. This analysis revealed that the absorber layer’s optimum bandgap value has to be 1.4 eV to achieve maximum efficiency of 22.57%. Subsequently, output solar cell parameters were analyzed as a function of CIGS layer thickness, defect density, and the operating temperature with an optimized n-Si layer. The newly modeled device has a p-CIGS/n-Si/In<sub>2</sub>S<sub>3</sub>/Al-ZnO structure. The main objective was to improve the overall cell performance while optimizing the thickness of absorber layers, defect density, bandgap, and operating temperature with the newly employed optimized n-Si layer. The increase of absorber layer thickness from 0.2 - 2 µm showed an upward trend in the cell’s performance, while the increase of defect density and operating temperature showed a downward trend in solar cell performance. This study illustrates that the proposed cell structure shows higher cell performances and can be fabricated on the lab-scale and industrial levels.展开更多
Defects in ZnO films grown by radio-frequency reactive magnetron sputtering under variable ratios between oxygen and argon gas have been investigated by using the monoenergetie positron beam technique. The dominate in...Defects in ZnO films grown by radio-frequency reactive magnetron sputtering under variable ratios between oxygen and argon gas have been investigated by using the monoenergetie positron beam technique. The dominate intrinsic defects in these ZnO samples are O vacancies （Vo） and Zn interstitials （Zni） when the oxygen fraction in the O2/Ar feed gas does not exceed 70% in the processing chamber. On the other hand, zinc vacancies are preponderant in the ZnO films fabricated in richer oxygen environment. The concentration of zinc vacancies increases with the increasing O2 fraction. For the oxygen fraction 85%, the number of zinc vacancies that could trap positrons will be smaller. It is speculated that some unknown defects could shield zinc vacancies. The concentration of zinc vacancies in the ZnO films varies with the oxygen fraction in the growth chamber, which is in agreement with the results of photolurninescence spectra.展开更多
Thin films of perovskite manganese oxide Lao.66Ca0.29K0.05MnO3（LCKMO） on Au/ITO（ITO=indium tin oxide） substrates were prepared by off-axis radio frequency magnetron sputtering and characterized by X-ray diffrac- t...Thin films of perovskite manganese oxide Lao.66Ca0.29K0.05MnO3（LCKMO） on Au/ITO（ITO=indium tin oxide） substrates were prepared by off-axis radio frequency magnetron sputtering and characterized by X-ray diffrac- tion（XRD）, high-resolution transmission electron microscopy（HRTEM）, and conductive atomic force microscopy （C-AFM） at room temperature. The thin films with thickness ranged from 100 nm to 300 nm basically show cubic structures with a=0.3886 nm, the same as that of the raw material used, but the structures are highly modulated. C-AFM results revealed that the atomic scale p-n junction feature of the thin films was the same as that of the single crystals. The preparation of the thin films thus further confirms the possibility of their application extending from micrometer-sized single crystals to macroscopic thin film.展开更多
Nitrogen-doped ZnO （ZnO：N） films are prepared by thermal oxidation of sputtered Zn3N2 layers on A1203 substrates. The correlation between the structural and optical properties of ZnO：N films and annealing temperat...Nitrogen-doped ZnO （ZnO：N） films are prepared by thermal oxidation of sputtered Zn3N2 layers on A1203 substrates. The correlation between the structural and optical properties of ZnO：N films and annealing temperatures is investigated. X-ray diffraction result demonstrates that the as-sputtered Zn3N2 films are transformed into ZnO：N films after annealing above 600℃. X-ray photoelectron spectroscopy reveals that nitrogen has two chemical states in the ZnO：N films： the No acceptor and the double donor （N2）o. Due to the No acceptor, the hole concentration in the film annealed at 700℃ is predicted to be highest, which is also confirmed by Hall effect measurement. In addition, the temperature dependent photoluminescence spectra allow to calculate the nitrogen acceptor binding energy.展开更多
Viscous aqueous solutions of chitosan and polyvinyl alcohol (PVA) were blended to enhance miscibility and avoid polymer phase separation. The mixtures were drop-casted and air dried to yield composite film materials t...Viscous aqueous solutions of chitosan and polyvinyl alcohol (PVA) were blended to enhance miscibility and avoid polymer phase separation. The mixtures were drop-casted and air dried to yield composite film materials that were characterized by equilibrium water uptake, physical stability in aqueous solution, and thermal stability. Chitosan/PVA blends have greater thermal stability, unique morphology, and reduced solubility in acidic solution, thus extending the useful pH range for chitosan as a sorbent material. The uptake properties of the films was investigated using methylene blue (MB) and a p-nitrophenol (PNP) dyes, where it was found that each single component polymer has greater uptake toward MB than PNP. A direct relationship between film composition (chitosan:PVA) with solution pH and the uptake of MB was observed. The results are in agreement with electrostatic interactions and contributions due to the hydrophobic effect for such composite materials.展开更多
We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of...We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.展开更多
The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typi...The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typically one micron in size. Focus is made on the dominant band of “super-hot” emission appearing in the spectral region located in energy above the fundamental absorption edge of a CdTe bulk crystal. A theoretical model has been developed that assumes the existence of a space-charge layer inside a microcrystal, which leads to the formation of a triangular potential well for an electron near the surface. The anomalous emission band arises as a result of the optical transitions of electrons from near-surface levels of spatial quantization to valence band states.展开更多
由单一还原剂 NaH_2PO_2或 NaH_2PO_3与 KBH_4的复合还原剂分别在类镍溶液中获得 Ni-Fe-P 以及 Ni-Fe-P-B 合金膜,研究了这些新型合金膜的磁性。结果发现,铁磁性元素 Fe 含量增加导致原子平均磁矩及饱和磁化强度 Ms 增大;结构为非晶态...由单一还原剂 NaH_2PO_2或 NaH_2PO_3与 KBH_4的复合还原剂分别在类镍溶液中获得 Ni-Fe-P 以及 Ni-Fe-P-B 合金膜,研究了这些新型合金膜的磁性。结果发现,铁磁性元素 Fe 含量增加导致原子平均磁矩及饱和磁化强度 Ms 增大;结构为非晶态的合金膜具有较优的矫顽力 Hc 值;合金膜磁滞回线出现较低的矩形比说明化学镀制备态样品不够均匀;热处理温度高于400℃后,合金膜的饱和磁化强度连续减小,矫顽力急剧增大;同时,镀层的均匀性明显得到改善。展开更多
文摘We report the performances of a chalcopyrite Cu(In, Ga)Se<sub>2 </sub>CIGS-based thin-film solar cell with a newly employed high conductive n-Si layer. The data analysis was performed with the help of the 1D-Solar Cell Capacitance Simulator (1D-SCAPS) software program. The new device structure is based on the CIGS layer as the absorber layer, n-Si as the high conductive layer, i-In<sub>2</sub>S<sub>3</sub>, and i-ZnO as the buffer and window layers, respectively. The optimum CIGS bandgap was determined first and used to simulate and analyze the cell performance throughout the experiment. This analysis revealed that the absorber layer’s optimum bandgap value has to be 1.4 eV to achieve maximum efficiency of 22.57%. Subsequently, output solar cell parameters were analyzed as a function of CIGS layer thickness, defect density, and the operating temperature with an optimized n-Si layer. The newly modeled device has a p-CIGS/n-Si/In<sub>2</sub>S<sub>3</sub>/Al-ZnO structure. The main objective was to improve the overall cell performance while optimizing the thickness of absorber layers, defect density, bandgap, and operating temperature with the newly employed optimized n-Si layer. The increase of absorber layer thickness from 0.2 - 2 µm showed an upward trend in the cell’s performance, while the increase of defect density and operating temperature showed a downward trend in solar cell performance. This study illustrates that the proposed cell structure shows higher cell performances and can be fabricated on the lab-scale and industrial levels.
基金Supported by the National Natural Science Foundation of China under No 10425072.
文摘Defects in ZnO films grown by radio-frequency reactive magnetron sputtering under variable ratios between oxygen and argon gas have been investigated by using the monoenergetie positron beam technique. The dominate intrinsic defects in these ZnO samples are O vacancies （Vo） and Zn interstitials （Zni） when the oxygen fraction in the O2/Ar feed gas does not exceed 70% in the processing chamber. On the other hand, zinc vacancies are preponderant in the ZnO films fabricated in richer oxygen environment. The concentration of zinc vacancies increases with the increasing O2 fraction. For the oxygen fraction 85%, the number of zinc vacancies that could trap positrons will be smaller. It is speculated that some unknown defects could shield zinc vacancies. The concentration of zinc vacancies in the ZnO films varies with the oxygen fraction in the growth chamber, which is in agreement with the results of photolurninescence spectra.
基金Supported by the National Natural Science Foundation of China(No.90922034)
文摘Thin films of perovskite manganese oxide Lao.66Ca0.29K0.05MnO3（LCKMO） on Au/ITO（ITO=indium tin oxide） substrates were prepared by off-axis radio frequency magnetron sputtering and characterized by X-ray diffrac- tion（XRD）, high-resolution transmission electron microscopy（HRTEM）, and conductive atomic force microscopy （C-AFM） at room temperature. The thin films with thickness ranged from 100 nm to 300 nm basically show cubic structures with a=0.3886 nm, the same as that of the raw material used, but the structures are highly modulated. C-AFM results revealed that the atomic scale p-n junction feature of the thin films was the same as that of the single crystals. The preparation of the thin films thus further confirms the possibility of their application extending from micrometer-sized single crystals to macroscopic thin film.
基金Supported by the National Natural Science Foundation of China under Grant No 50532070
文摘Nitrogen-doped ZnO （ZnO：N） films are prepared by thermal oxidation of sputtered Zn3N2 layers on A1203 substrates. The correlation between the structural and optical properties of ZnO：N films and annealing temperatures is investigated. X-ray diffraction result demonstrates that the as-sputtered Zn3N2 films are transformed into ZnO：N films after annealing above 600℃. X-ray photoelectron spectroscopy reveals that nitrogen has two chemical states in the ZnO：N films： the No acceptor and the double donor （N2）o. Due to the No acceptor, the hole concentration in the film annealed at 700℃ is predicted to be highest, which is also confirmed by Hall effect measurement. In addition, the temperature dependent photoluminescence spectra allow to calculate the nitrogen acceptor binding energy.
文摘Viscous aqueous solutions of chitosan and polyvinyl alcohol (PVA) were blended to enhance miscibility and avoid polymer phase separation. The mixtures were drop-casted and air dried to yield composite film materials that were characterized by equilibrium water uptake, physical stability in aqueous solution, and thermal stability. Chitosan/PVA blends have greater thermal stability, unique morphology, and reduced solubility in acidic solution, thus extending the useful pH range for chitosan as a sorbent material. The uptake properties of the films was investigated using methylene blue (MB) and a p-nitrophenol (PNP) dyes, where it was found that each single component polymer has greater uptake toward MB than PNP. A direct relationship between film composition (chitosan:PVA) with solution pH and the uptake of MB was observed. The results are in agreement with electrostatic interactions and contributions due to the hydrophobic effect for such composite materials.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374033,11774030,51735001 and 61775016the Fundamental Research Funds for the Central Universities under Grant No 2017CX10007
文摘We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.
文摘The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typically one micron in size. Focus is made on the dominant band of “super-hot” emission appearing in the spectral region located in energy above the fundamental absorption edge of a CdTe bulk crystal. A theoretical model has been developed that assumes the existence of a space-charge layer inside a microcrystal, which leads to the formation of a triangular potential well for an electron near the surface. The anomalous emission band arises as a result of the optical transitions of electrons from near-surface levels of spatial quantization to valence band states.
文摘由单一还原剂 NaH_2PO_2或 NaH_2PO_3与 KBH_4的复合还原剂分别在类镍溶液中获得 Ni-Fe-P 以及 Ni-Fe-P-B 合金膜,研究了这些新型合金膜的磁性。结果发现,铁磁性元素 Fe 含量增加导致原子平均磁矩及饱和磁化强度 Ms 增大;结构为非晶态的合金膜具有较优的矫顽力 Hc 值;合金膜磁滞回线出现较低的矩形比说明化学镀制备态样品不够均匀;热处理温度高于400℃后,合金膜的饱和磁化强度连续减小,矫顽力急剧增大;同时,镀层的均匀性明显得到改善。
