Selenium and Sulphur replacement dynamics in CZTSSe and CZGSSe kesterite materials

The replacement dynamics of Se by S is investigated in kesterite Cu2ZnSn(S,Se)(4) and Cu2ZnGe(S,Se)(4). Two different post-sulphurization techniques yield the same results. In the initial stages of the replacement, the original selenium-rich phase coexists with a second mixed phase. This phase has an increased sulphur content of 30 %. In later stages of the reaction, the initial phase disappears in favor of the second phase. Thus, sulphur inclusions of less than 30 % seem impossible while above 30 % the sulphur amount is adjustable.