Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our wo...Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.展开更多
The electronic band structures, densities of states （DOSs）, and projected densities of states （PDOSs） of the wurtzite In1-xGaxN with x=0, 0.0625, 0.125 are studied using the generalized-gradient approximation （GG...The electronic band structures, densities of states （DOSs）, and projected densities of states （PDOSs） of the wurtzite In1-xGaxN with x=0, 0.0625, 0.125 are studied using the generalized-gradient approximation （GGA） and GGA＋U in density functional theory. Our calculations suggest that in the case of wurtzite InN it is important to apply an on-site Hubbard correction to both the d states of indium and the p states of nitrogen in order to recover the correct energy level symmetry and obtain a reliable description of the InN band structure. The method is used to study the electronic properties of the wurtzite In1-xGaxN. The conduction band minimum （CBM） energy increases, while the valence band maximum （VBM） energy decreases with the increase of the gallium concentration. The effect leads to broadening the band gap （BG） and the valence band width （VBW）. Furthermore, the compressive strain in the crystal can cause the BG and the VBW to increase with the increase of gallium concentrations.展开更多
Electronic structures and optical properties of single-layer In1-xGaxN are studied by employing Heyd-Scuseria-Ernzerh（HSE） method based on the first-principles. The band structure and density of states（DOS） of sin...Electronic structures and optical properties of single-layer In1-xGaxN are studied by employing Heyd-Scuseria-Ernzerh（HSE） method based on the first-principles. The band structure and density of states（DOS） of single-layer In1-xGaxN are calculated, and the band gap ranges from 1.8 eV to 3.8 eV as the ratio x changes, illustrating the potential for the tunability of band gap values via Ga doped. We also have investigated optical properties of single-layer In1-xGaxN such as dielectric function, refractive index and absorption coefficient, the main peak of dielectric function spectrum and the absorption edge are found to have a remarkable blue-shift as the concentration of Ga increases. Furthermore, the optical properties of single-layer In1-xGaxN are analyzed based on the band structures and DOS analysis. Such unique optical properties have profound application in nanoelectronics and optical devices.展开更多
文摘Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.
基金Project supported by the National Natural Science Foundation of China(Grant No.50971094)the Natural Science Foundation of Beijing,China(Grant Nos.KZ201310028032 and 1092007)the Domestic Visiting Program for the Graduate Students of Inner Mongolia University,China
文摘The electronic band structures, densities of states （DOSs）, and projected densities of states （PDOSs） of the wurtzite In1-xGaxN with x=0, 0.0625, 0.125 are studied using the generalized-gradient approximation （GGA） and GGA＋U in density functional theory. Our calculations suggest that in the case of wurtzite InN it is important to apply an on-site Hubbard correction to both the d states of indium and the p states of nitrogen in order to recover the correct energy level symmetry and obtain a reliable description of the InN band structure. The method is used to study the electronic properties of the wurtzite In1-xGaxN. The conduction band minimum （CBM） energy increases, while the valence band maximum （VBM） energy decreases with the increase of the gallium concentration. The effect leads to broadening the band gap （BG） and the valence band width （VBW）. Furthermore, the compressive strain in the crystal can cause the BG and the VBW to increase with the increase of gallium concentrations.
基金supported by the National Natural Science Foundation of China (No.11404230)Foundation of Science and Technology Bureau of Sichuan Province (No.2013JY0085)
文摘Electronic structures and optical properties of single-layer In1-xGaxN are studied by employing Heyd-Scuseria-Ernzerh（HSE） method based on the first-principles. The band structure and density of states（DOS） of single-layer In1-xGaxN are calculated, and the band gap ranges from 1.8 eV to 3.8 eV as the ratio x changes, illustrating the potential for the tunability of band gap values via Ga doped. We also have investigated optical properties of single-layer In1-xGaxN such as dielectric function, refractive index and absorption coefficient, the main peak of dielectric function spectrum and the absorption edge are found to have a remarkable blue-shift as the concentration of Ga increases. Furthermore, the optical properties of single-layer In1-xGaxN are analyzed based on the band structures and DOS analysis. Such unique optical properties have profound application in nanoelectronics and optical devices.
