Control over the Gallium Depth Profile in 30×30 cm2Sequentially Processed CIGS

In order to control the bandgap profile of CIGSe absorbers, several key parameters of the absorber formation process have been investigated using semi-industrial 30×30 cm2 chalcogenization equipment. It was found that the degree of gallium-indium interdiffusion depends on the thermal budget of the process and on the selenium vapor pressure at the utilized high process temperature. Additionally, it depends on the copper and sodium content of the precursor. As a result, the gallium depth profile could accurately be controlled and the minimum bandgap could be varied between 1.02 eV and 1.13 eV.