A promising sputtering route for one-step fabrication of chalcopyrite phase Cu(In,Ga)Se2 absorbers without extra Se supply

One-step fabrication of the chalcopyrite Cu(In,Ga)Se2 (CIGS) absorber layer without excess Se supply during/after deposition or post-selenization treatments is reported. By using pulse DC sputtering from a single quaternary CIGS target, the chalcopyrite structure is spontaneously developed on the substrate at 500 °C even without extra Se supply. The obtained CIGS absorber layer possesses columnar grains with (112) preferred orientation. Device efficiency of 8.22% is observed for slightly Se-deficient CIGS films. By further tuning the target composition, the efficiency is enhanced to 10.14%. We demonstrate that the device-quality CIGS absorber can be formed even in the Se-deficient environment and further improvement of efficiency can be achieved by tuning the Se content of the target. Accordingly, our one-step sputtering process shows great potential for mass production of thin film CIGS solar cells with a low cost and a high throughput.