Experimental study of p layers in ‘‘tunnel’’ junctions for high efficiency amorphous silicon alloy multijunction solar cells and modules

The role of the p layer in the formation of good quality ‘‘tunnel’’ junctions and its dependence on the attainment of high efficiency hydrogenated amorphous silicon alloy (a‐Si:H) multijunction cells has been investigated. A new technique, namely, the evaluation of the current‐voltage characteristics of the NIPN structure consisting of a single‐junction n‐i‐p cell with an overlying doped n layer, has been developed for the determination of losses at the ‘‘tunnel’’ junction. Using an optimized p layer, an initial conversion efficiency of 11.4% has been obtained on a double junction a‐Si:H module of aperture area ∼900 cm2.