Increasing surface band gap of Cu(In,Ga)Se_2 thin films by post depositing an In-Ga-Se thin layer

We have developed a simple approach to fabricate wide band gap surface layer for Cu(In,Ga)Se2 (CIGS) thin film. The Cu depleted surface layer was reconstructed by an In-Ga-Se post deposition treatment at different temperatures, which was monitored by a light controlling method. A desirable Cu concentration in surface layer has been achieved after depositing a 80 nm thick In-Ga-Se layer at 400°C and the corresponding device performance is remarkably improved compared with device without surface modification. Additionally, the excess Cu(2-x)Se phase on the surface could also be eliminated by this method in case of high Cu/(In+Ga).