Electronic, optical, and mechanical properties of Cu2ZnSnS4 with four crystal structures

The structural, electronic, optical, and mechanical properties of Cu2ZnSnS4 with four crystal structures are calculated using the density functional theory. No significant difference is observed between the calculated optical and mechanical properties of the considered four crystal structures. The calculated results are in agree- ment with available reported experimental data. According to the calculated results, the fundamental band gap of Cu2ZnSnS4 is mainly determined by the bandwidth of the isolated conduction band. The effective-mass of carriers of Cu2ZnSnS4 are very small, especially the effective-mass of electrons on the bottom of the conduction band of zincblende-derived Cu2ZnSnS4. Using the calculated elastic constants matrix, the Born stability criteria is shown to be satisfied, and the high B/G ratio indicates that Cu2ZnSnS4 is prone to ductile behavior.