The effect of Mo back contact on Na out-diffusion and device performance of Mo/Cu(In,Ga)Se/sub 2//CdS/ZnO solar cells

Molybdenum thin films were deposited on soda lime glass (SLG) substrates using direct-current planar magnetron sputtering, with a sputtering power density of 1.2 W/cm/sup 2/. The working gas (Ar) pressure was varied from 0.6 to 16 mtorr to induce changes in the Mo films' morphology and microstructure. Thin films of Cu(In,Ga)Se/sub 2/ (CIGS) were deposited on the Mo-coated glass using the 3-stage co-evaporation process. The morphology of both the Mo-coated SLG and the CIGS thin films grown on it was examined using high-resolution scanning electron microscopy. Na was depth profiled in the Mo and CIGS films by secondary ion mass spectrometry. The device performance was evaluated under standard conditions of 1000 W/m/sup 2/ and 25/spl deg/C. Optimum device performance is found for an intermediate Mo sputtering pressure.