Cu(In,Ga)Se 2 :Te Thin Films for Stoichiometric Compensation by Using Co-Sputtering and Rapid Thermal Annealing †.

Improvement in crystallinity was investigated by compensating for stoichiometric deviations of non-selenization processed Cu_0.9In_0.7Ga_0.3Se₂ (CIGS) thin films due to highly volatile Se by co-sputtering them with Te followed by rapid thermal annealing. The prepared CIGS:Te thin films did not show any linear correlation between the compositional ratio and the co-sputtering time of Te; however, the deviation parameter (Δs) from the stoichiometry and normalized stoichiometric deviations of Se + Te and In + Ga were largely consistent with the behavior of thin-film properties. The proposed method provides better crystallinity with a large grain size, clear grain boundaries, and low microstrain and dislocation density, resulting in a large volume of the unit cell. The CIGS:Te thin films used as absorbers show improved optical properties compared to the conventional CIGS thin films, with E_g = 1.548 eV. These results can advance the low-cost commercialization of the enhanced-efficiency CIGS:Te thin films without the selenization process. [ABSTRACT FROM AUTHOR]