Cu(In,Ga)Se₂:Te Thin Films for Stoichiometric Compensation by Using Co-Sputtering and Rapid Thermal Annealing

Abstract

Improvement in crystallinity was investigated by compensating for stoichiometric deviations of non-selenization processed Cu0.9In0.7Ga0.3Se2 (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 Eg = 1.548 eV. These results can advance the low-cost commercialization of the enhanced-efficiency CIGS:Te thin films without the selenization process.

Keywords

• CIGS:Te thin films
• non-selenization
• co-sputtering
• Cu_0.9In_0.7Ga_0.3Se₂ (CIGS) target
• Te target
• rapid thermal annealing