Cu2ZnSn(S,Se)4 (CZTSSe) alloys have attracted much attention for solar cell applications due to their optimal band gap, higher absorption coefficient, and earth abundant constituents. However, the solar conversion efficiency of CZTSSe solar cells are still low in comparison with other solar cells based on Cu(In,Ga)Se2 and CdTe due to their low open-circuit voltage. In this work, we perform first-principles density functional calculation to study stability and electronic structure of CZTS and CZTSe polytypes using the hybrid density functional (HSE). We find that (i) the polytype with the higher electronic band gap is easier to be formed. (ii) The kesterite phase is the most stable phase with the highest electronic band gap among the polytypes; (iii) the PMCA phase is the least stable, and has the lowest band gap. An Ising model is developed to model other polytypes. Finally, the electronic structure of several polytypes is discussed in comparison with binary and ternary semiconductors.

Hybrid functional study of stability and electronic structure of Cu2ZnSn(S,Se)4 polytypes

249th National Meeting (2015)

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