| Copper-zinc-tin-sulfur(CZTS)quaternary compound has variety inorganic components,complex crystal structure.As a multi-compound thin film solar cell core absorption layer material,it's very easy to generate hybrids.This paper is based on Yu's solid and molecular empirical electron theory(EET)to calculate the valence electron structure of the copper-zinc-tin-sulfur quaternary compound system,using the calculating method of Bond Length Difference.The calculation includes unit phase Cu,Zn and Sn,binary phase ZnS,CuS,SnS and CuZn,and CZTS quaternary phase(Kesterite,Stannite and PMCA).In this paper,based on the valence electron structure parameters given by the EET theory and the BLD calculation,the bond energy of all the covalent bonds in the above phases is calculated,and the total bond energy of each phase is calculated.By constructing supercells and designing crystal defects,the influence of different concentration transposition defects and vacancy defects on the stability of alloy phase was calculated and discussed,drawing the following conclusions.When the ratio of atomic is 2:1:1:4,the stability of the quaternary phase can be determined by the strongest bond energy or the total bond energy.More stable,more easily generated.The results are both shown to be quaternary phase is more stable and easier to generate.The results are as follows.When the heterogeneous product contains ZnS or CuZn,the tetragonal bond strength intensity is relatively close,more likely to produce heterogeneous phase.In order to discuss the effect of the defect on the phase stability under the condition of unbalanced state,multiple supercells were designed and the transposition defects and vacancy defects were added.When the crystal defects are transposition defects,the total bond energy of the calculated supercell gets higher and lower with the doping concentration for the pure phase.The total bond energy of no doping is 3.99 × 104kJ/mol.When the atom ratio of Cu/Zn is 14/10,the total bond energy is 3.83 × 104kJ/mol.When the ratio is reduced to 14/10,the energy gains to 3.89 × 104kJ/mol.When the alloy of the same atomic ratio is present in a mixed state of different heterogeneous phases,the total bond energy are 3.89 × 104kJ/mol,3.83 × 104kJ/mol and 3.43 × 104kJ/mol.It is presumed that when the atomic ratio reaches 14/10,and the Cu/Zn ratio reaches 14/18,there will be hyphis in the system.When the system defects are vacancy defects,the total energy of supercell is 3.16 × 104kJ/mol.It can be seen that the effect of phase stability on the phase stability is more obvious.This paper explains the direct cause of the effect of the vacancy defect on the crystal structure in terms of the thermodynamics function.The research content of this paper is mainly based on EET theory and its thinking and BLD method.The phase stability of the pure phase and the mixed phase of the Cu-Zn-Sn-quaternary compound system and its changing trend can be speculate from the valence electron structure and the thermodynamic function calculation results.And the results suits experimental very well.Proving that the simulation and calculation methods of this paper can be further extended to the correlation calculation of the same type of multivariate compounds.It can provide the auxiliary and guidance for experimental preparation... |
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