Theoretical investigation of CdIn2S4 : A possible substitute for CdS in CuIn1−xGaxSe2 -based photovoltaic devices

Herein we report a theoretical investigation based on density-functional theory (DFT) calculations devoted to the nature of charge carriers in $\mathrm{CdI}{\mathrm{n}}_{2}{\mathrm{S}}_{4}$. Our simulations led to unambiguous results concerning the origin of $n$-type semiconductivity and its magnitude in this material. Namely, the calculated defect formation energies demonstrate that the cadmium substoichiometry is more favorable than the indium one to account for $n$-type conductivity. Moreover, the anionic vacancies would not be the driving force of the occurring processes but a sulfur-poor atmosphere has to be privileged compared to a sulfur-rich one to favor the formation of $\mathrm{CdI}{\mathrm{n}}_{2}{\mathrm{S}}_{4}$ with understoichiometry in Cd(II) and thus achieve a higher concentration of free electrons at room temperature.