Effects Of Atomic Vacancy And Temperature On The Physical Properties Of Group Ⅰ-Ⅲ-Ⅵ Compounds

Group I-III-V alloys are important thin-film solar cell materials.In addition to chalcopyrite CuGaS₂ as a promising light collection material for intermediate-band solar cells,other structures with a stoichiometric ratio of Cu and Ga other than 1:1 also have great potential,and the atoms in the Cu-Ga-S system vacancies usually exist in other stoichiometric structures other than chalcopyrite structures,and are expected to have a decisive influence on structural stability and electronic structure.Using ab initio evolutionary variable combinatorial search,Monte Carlo simulation,and special quasi-random structure methods,the order of atomic vacancies can be studied by fully identifying stable structures and stoichiometric ratios.Under the premise of fully determining the structure of non-1:1 stoichiometric ratio under different pressures,it also shows the influence of order on the electronic band structure of chalcopyrite structure.The current work has the following innovative results:1.By comparing the energy of the same component structure with vacancies,it is found that the structure with a linear arrangement tends to have lower energy than the structure with a zigzag arrangement.Comparing the structure of different components,it is found that the orderly arrangement of the atomic vacancies locally forming a straight line can make the structure more stable by reducing the formation energy.2.The structure search found that the new van der Waals layered P2₁/c-Cu₂S phase has better optical properties than the newly discovered ground state P4₂-Cu₂S.The stability of the P2₁/c-Cu₂S phase is judged and the band gap value is calculated to be1.09 e V.The proper band gap and direct band gap characteristics make it a potential candidate material for solar cells.3.By calculating the band gap changes of different components of the structure under different pressures,the p-d coupling between S and Cu atoms is used to explain the abnormal changes in the band gap of the structure caused by pressure.4.The Monte Carlo simulation of the chalcopyrite structure and the results of the special quasi-random structure further show that by controlling the order parameters determined by the synthesis conditions（annealing time）,the band gap of CuGaS₂can be changed from 2.51 e V of the chalcopyrite phase Continuously tune to 0.13 e V in a completely disordered configuration.The paper has 16 figures,6 tables,and 94 references.