Electronic and optical properties of substitutional V, Cr and Ir impurities in Cu2ZnSnS4

• Doping with V, Cr and Ir in the natural and synthetic Cu2ZnSnS4 is analyzed.
• The electronic structure is characterized for intermediate bands within of the energy band gap.
• It leads to additional photon absorption and emission channels
• These properties could therefore be used for novel optoelectronic devices.

The substitution of cation atoms by V, Cr and Ir in the natural and synthetic quaternary Cu2ZnSnS4 semiconductor is analyzed using first-principles methods. In most of the substitutions, the electronic structure of these modified CZTS is characterized for intermediate bands with different occupation and position within of the energy band gap. A study of the symmetry and composition of these intermediate bands is carried out for all substitutions.These bands permit additional photon absorption and emission channels depending on their occupation. The optical properties are obtained and analyzed. The absorption coefficients are split into contributions from the different absorption channels and from the inter- and intra-atomic components. The sub bandgap transitions are significant in many cases because the anion states contribute to the valence, conduction and intermediates bands. These properties could therefore be used for novel optoelectronic devices.