Influence of surface-modified Mo back contact on post-selenized Cu(In,Ga)Se2 thin films

In this work, the influences of surface-modified Mo back contacts on the morphology of Cu layers and quality of Cu(In,Ga)Se2 (CIGS) thin films are investigated. One method of sputtering treatment to modify the Mo surface effectively improved the adhesion between the Cu and Mo layers. However, Cu layers electrodeposited on the various modified Mo surfaces created different morphological structures, which impacted the CIGS thin films. First, an alloyed Cu-In-Ga film based on the Cu layer of smooth structure would experience homogeneous element diffusion compared to the Cu layer of the rugged structure. Second, the CIGS film based on the smooth Cu-covered substrate exhibited a uniform surface profile with regular crystals, while the CIGS film based on a rugged one exhibited an uneven surface profile with several irregular crystals. Additionally, the smooth Cu-covered substrate reduced the adverse phase separation of CuInSe2 and CuGaSe2 more effectively.