Sodium co-evaporation for low temperature Cu(In,Ga)Se-2 deposition

Cu(In,Ga)Se-2 (CIGS) thin-films were deposited 'in-line', i.e. the substrat e is moved with respect to the sources on soda-lime glass (SLG). To better understand the role of substrate temperature during CIGS deposition, we suc cessively decreased the substrate temperature. The CIGS layers were analyse d using sheet resistance measurements, SEM and XRD in addition, solar cell devices were prepared. We found significant deterioration in solar cell par ameters and a different morphology with decreasing substrate temperature. T he results were compared with the results from CIGS layers and devices grow n on sodium free glass. In a second step, a sodium evaporation source was a dded to the deposition system to provide additional sodium during film grow th. With this technique, solar cells (0.5 cm(2)) with efficiencies of 11.7% (SLG) and 10.9% (Na-free glass) were fabricated 'in-line' at a substrate t emperature of 400 degreesC. (C) 2001 Elsevier Science B.V. All rights reser ved.