In or Ga gradients in the Cu(In1-xGax)Se2(CIGS)absorbing layer lead to change the lattice parameters of the absorbing layer,giving rise to the bandgap grading in the absorbing layer which is directly associated with t...In or Ga gradients in the Cu(In1-xGax)Se2(CIGS)absorbing layer lead to change the lattice parameters of the absorbing layer,giving rise to the bandgap grading in the absorbing layer which is directly associated with the degree of absorbing ability of the CIGS solar cell.We tried to characterize the depth profile of the lattice parameters of the CIGS absorbing layer using a glancing incidence X-ray diffraction(GIXRD)technique,and then investigate the bandgap grading of the CIGS absorbing layer.When the glancing incident angle increased from 0.50 to 5.00°,the a and c lattice parameters of the CIGS absorbing layer gradually decreased from 5.7776(3)to 5.6905(2)?,and 11.3917(3)to 11.2114(2)?,respectively.The depth profile of the lattice parameters as a function of the incident angle was consistent with vertical variation in the compositionof In or Ga with depth in the absorbing layer.The variation of the lattice parameters was due to the difference between the ionic radius of In and Ga co-occupying at the same crystallographic site.According to the results of the depth profile of the refined parameters using GIXRD data,the bandgap of the CIGS absorber layer was graded over a range of 1.222-1.532 eV.This approach allows to determine the In or Ga gradients in the CIGS absorbing layer,and to nondestructively guess the bandgap depth profile through the refinement of the lattice parameters using GIXRD data on the assumption that the changes of the lattice parameters or unit-cell volume follow a good approximation to Vegard’s law.展开更多
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
基金supported by Korea Research Institute of Standards and Science(KRISS–2019–GP2019-0014)。
文摘In or Ga gradients in the Cu(In1-xGax)Se2(CIGS)absorbing layer lead to change the lattice parameters of the absorbing layer,giving rise to the bandgap grading in the absorbing layer which is directly associated with the degree of absorbing ability of the CIGS solar cell.We tried to characterize the depth profile of the lattice parameters of the CIGS absorbing layer using a glancing incidence X-ray diffraction(GIXRD)technique,and then investigate the bandgap grading of the CIGS absorbing layer.When the glancing incident angle increased from 0.50 to 5.00°,the a and c lattice parameters of the CIGS absorbing layer gradually decreased from 5.7776(3)to 5.6905(2)?,and 11.3917(3)to 11.2114(2)?,respectively.The depth profile of the lattice parameters as a function of the incident angle was consistent with vertical variation in the compositionof In or Ga with depth in the absorbing layer.The variation of the lattice parameters was due to the difference between the ionic radius of In and Ga co-occupying at the same crystallographic site.According to the results of the depth profile of the refined parameters using GIXRD data,the bandgap of the CIGS absorber layer was graded over a range of 1.222-1.532 eV.This approach allows to determine the In or Ga gradients in the CIGS absorbing layer,and to nondestructively guess the bandgap depth profile through the refinement of the lattice parameters using GIXRD data on the assumption that the changes of the lattice parameters or unit-cell volume follow a good approximation to Vegard’s law.
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.
