Advances in cell and module efficiency of a-si:h based triple-junction solar cells made using roll-to-roll deposition

Over the last several years, we have continuously increased the conversion efficiency of solar cells and modules. In this paper, we discuss new developments which led to a ~5% increase in conversion efficiency of cells and modules made using roll-to-roll deposition. The enhanced efficiency is attributed primarily to the replacement of the conventional Al/ZnO back reflector with a new Ag/ZnO structure. We optimized the deposition parameters to obtain the highest cell efficiency. We used large-area cells to fabricate flexible interconnected modules of dimensions 548.6 cm × 39.4 cm. The initial power output (P_max) of the modules was 180.2-183.3 W which is the highest obtained for roll-to-roll processing. We conducted light soak studies to determine stable module power output.