First-principles Study on Electronic and Optical Properties of Kesterite and Stannite Cu_2ZnSnS_4 Photovoltaic Absorbers

摘要

To find the optical properties of Cu_2ZnSnS_4 (CZTS) absorber in two crystal structures (kesterite and stannite) which are key factors determining solar cell performance and are based on the electronic structures, a systematical calculation of electronic and optical properties were calculated using density functional theory. The results suggested that the optical properties of CZTS had a rather weak dependence on the (Cu, Zn) cation ordering. Kesterite and stannite CZTS both suited for photovoltaics with large light absorption coefficient ( ＞ 10~4 cm~(-1) ) in the visible light region that is the most important part for photovoltaics, and kesterite CZTS had larger light absorption than stannite CZTS exhibiting a more obvious advantage. In the visible light region the reflectivity of CZTS was lower than that of silicon, the absorber material used most widely, which might be in favor of light absorption and cell efficiency. Ground-state structure, electronic transitions relevant to solar light absorption, static dielectric constant and plasma frequency were also investigated.