The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the...The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.展开更多
Impurity formation energy, electronic structure, and photocatalytic properties of C-, N-, or S-doped BiOCl are investigated by density-functional theory plus U calculations(DFT + U). Results show that the doping effec...Impurity formation energy, electronic structure, and photocatalytic properties of C-, N-, or S-doped BiOCl are investigated by density-functional theory plus U calculations(DFT + U). Results show that the doping effect of S is better than that of C or N on the tunable photocatalytic activities of BiOCl. At low concentration, S-doped BiOCl systems are the most stable under Bi-rich growth conditions because of their lower impurity-formation energy. Compared with the electronic structures of S-doped BiOCl, C-or N-doped BiOCl have relatively deeper impurity energy levels appearing in their band gap(except Bi_(36)O_(35)NCl_(36)), which may act as photogenerated carrier-recombination centers and reduce photocatalytic activity. At high concentration, S is substituted on the O lattice site system, whereas some S 3p states mix with the valence band; this mixture leads to an obvious band-gap decrease and continuum-state formation above the valence-band edge of BiOCl. Such activity is advantageous to photochemical catalysis response. Compared with pure Bi OCl and a low-concentration S-doped system, a high-concentration S-doped system shows an obvious redshift on the absorption edge and has better photocatalytic O_2 evolution performance.展开更多
The title complex was synthesized by the reaction of taurine 、salicylic and potassium hydrate in water ethanol solution. The crystal structure was determined by X ray diffraction method and the chemical formula weigh...The title complex was synthesized by the reaction of taurine 、salicylic and potassium hydrate in water ethanol solution. The crystal structure was determined by X ray diffraction method and the chemical formula weight of the complex is 267.34. and the crystal belongs to monoclinic system with space group P21/c and cell parameters: a=2.0292(8)nm, b=0.7283(4)nm, c=0.7540(4)nm; β=94.15(1)°, V=1.1115(9)nm3, Z=4, Dc=1.598 g·cm-3, μ=0.0663mm-1, F(000)=552. Thecomplex is a lamellar compound of infinite expansion. In addition, the complex has been tested for its antibacterial active. The average diameter of complex antibacterial activing cycle: colibacillus is 9mm, pseudomonas aeruginosa is 8mm. CCDC: 194630.展开更多
We have used an ab initio self-consistent field(SCF) molecular orbital approach toinvestigate the equilibrium geometry and relative stability of C4S4m- (m=0,1,2,3,4). We foundthat the geometry of anions studied from m...We have used an ab initio self-consistent field(SCF) molecular orbital approach toinvestigate the equilibrium geometry and relative stability of C4S4m- (m=0,1,2,3,4). We foundthat the geometry of anions studied from m=0 to m=4 changes from non-aromatic structure toaromatic structure and fmally anti-aromatic structure and that the relative stability decreases inthe order of: C4S4m- > C4S42- > C4S4 > C4S4 > C4S4.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)under grant nos.61574059 and 61722402the National Key Research and Development Program of China(2016YFB0700700)+1 种基金Shu-Guang program(15SG20)CC of ECNU
文摘The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.
基金This project was supported by the China Postdoctoral Science Foundation,Henan Postdoctoral Science Foundation,NCWU 2017 Annual Teaching Teacher Training Object ProjectKey Research Projects of Higher Education in Henan Province(18B150010)+1 种基金the Key Scientific Research Project of Henan Higher Education(No.17A520011)the Science and Technology Research Project of Henan Province(182102110029)
文摘Impurity formation energy, electronic structure, and photocatalytic properties of C-, N-, or S-doped BiOCl are investigated by density-functional theory plus U calculations(DFT + U). Results show that the doping effect of S is better than that of C or N on the tunable photocatalytic activities of BiOCl. At low concentration, S-doped BiOCl systems are the most stable under Bi-rich growth conditions because of their lower impurity-formation energy. Compared with the electronic structures of S-doped BiOCl, C-or N-doped BiOCl have relatively deeper impurity energy levels appearing in their band gap(except Bi_(36)O_(35)NCl_(36)), which may act as photogenerated carrier-recombination centers and reduce photocatalytic activity. At high concentration, S is substituted on the O lattice site system, whereas some S 3p states mix with the valence band; this mixture leads to an obvious band-gap decrease and continuum-state formation above the valence-band edge of BiOCl. Such activity is advantageous to photochemical catalysis response. Compared with pure Bi OCl and a low-concentration S-doped system, a high-concentration S-doped system shows an obvious redshift on the absorption edge and has better photocatalytic O_2 evolution performance.
文摘The title complex was synthesized by the reaction of taurine 、salicylic and potassium hydrate in water ethanol solution. The crystal structure was determined by X ray diffraction method and the chemical formula weight of the complex is 267.34. and the crystal belongs to monoclinic system with space group P21/c and cell parameters: a=2.0292(8)nm, b=0.7283(4)nm, c=0.7540(4)nm; β=94.15(1)°, V=1.1115(9)nm3, Z=4, Dc=1.598 g·cm-3, μ=0.0663mm-1, F(000)=552. Thecomplex is a lamellar compound of infinite expansion. In addition, the complex has been tested for its antibacterial active. The average diameter of complex antibacterial activing cycle: colibacillus is 9mm, pseudomonas aeruginosa is 8mm. CCDC: 194630.
文摘We have used an ab initio self-consistent field(SCF) molecular orbital approach toinvestigate the equilibrium geometry and relative stability of C4S4m- (m=0,1,2,3,4). We foundthat the geometry of anions studied from m=0 to m=4 changes from non-aromatic structure toaromatic structure and fmally anti-aromatic structure and that the relative stability decreases inthe order of: C4S4m- > C4S42- > C4S4 > C4S4 > C4S4.
