Electronic structure and lattice dynamics in kesterite-type Cu_2ZnSnSe_4 from first-principles calculations

摘要

Electronic band structure, densities of states, and the details of chemical bonding in Cu_2ZnSnSe_4, a compound used in photovoltaic applications and structurally close to chalcopyrite, has been studied using the siesta method within the local-density approximation of the density-functional theory. Calculated zone-center phonons for Cu_2ZnSnSe_4 in kesterite and stannite phases reveal a similarity to those in structurally close CuInSe_2, with some additional modes which must become observable due to the reduced crystal symmetry. The prediction that the highest TO vibration mode has predominantly Zn contribution is consistent with a strong Zn concentration dependence of this particular mode earlier observed in (Zn,Cd)-mixed kesterite systems. A detailed comparison of calculated vibration spectra for kesterite and stannite phases helps to identify the features which could be useful for distinguishing these two structures in practice.