Material and device consideration for high efficiency a-Si alloy-based multijunction cells

It is now well-recognized that multi-bandgap triple-junction structures offer the attractive potential of achieving high efficiency with good stability in amorphous silicon alloy solar cells. Although stable cell efficiency exceeding 11% has been demonstrated, significant improvement in our understanding of materials and devices is necessary to reach the goal of 16% stable cell efficiency. Choice of suitable precursors in the plasma and control of growth kinetics will play a key role in improving material property. Innovative device design to aid minority carrier transport will help in obtaining the highest efficiency from a given material. In this paper, the critical issues regarding the optimization of materials and devices to obtain high stable efficiency are discussed.