Current-voltage characteristics and IPCE curves of solar cells based on SQ01 ((a) and (b)) and SQ02 ((c) and (d)). The solid curves represent the cells using an Al/Al cathode, the dashed curves represent the cells using a Ca cathode. The dotted line in (b) and (d) represents the cell absorption. The thickness for SQ01 and SQ02 is 40 nm and 35 nm, respectively.