Effect of annealing on molybdenum films used as a back contact for Cu(In, Ga)Se2 solar cells

Mo films were deposited on SLG substrates by sputtering to observe the influence of substrate temperature (Tss) and post-deposition annealing on film structure and alkali diffusion. The Mo films were characterized by XRD and AFM, indicating an increase of the grain size and a decrease of the roughness with Tss. After annealing, the samples deposited at 100°C show smaller grain size and higher surface roughness. Secondary ion mass spectroscopy (SIMS) analysis were also performed, and indicated a decrease of the Na and K with increased Tss, with the smallest intensity for the samples deposited at 100°C. A 3-D numerical model was used for simulating the grain boundary diffusion.