Stability, electronic, and optical properties of wurtzite Cu_2Cd_xZn_(1-x)SnS_4 alloys as photovoltaic materials: First-principles insight

摘要

First-principles calculations have been performed to understand the structural and electronic properties of wurtzite (wz) phase of cation mixed Cu_2Cd_xZn_(1-x)SnS_4 (CCZTS) alloys which have a band gap that fits the requirement of a solar cell light absorber. We have used five different exchange correlations (XCs) to fix the structural parameters with high accuracy. The hybrid XC, which has been used to explain thermodynamical, electronic, and optical properties, shows very promising results. We find that (ⅰ) the CCZTS alloys are highly miscible with low formation enthalpies, (ⅱ) the band gap of CCZTS alloys can be tuned in the range 1.56-1.39 eV as Cd concentration (x) increases from 0.0 to 1.0 with a small bowing parameter b = 0.293 eV, and (ⅲ) the calculated band gap of CCZTS alloys decreases mainly due to the upshift of the valence band. Our predicted results are in agreement with the only available synthesized wz phase CCZTS data [Ramasamy et al., RSC Adv. 3, 1186 (2013)]. The dependence of the CCZTS alloys energy on growth temperature is also calculated. Our results could be very useful for growth of these materials.