Amorphous silicon solar cells

Abstract

This chapter will first describe, in Sect. 6.1, the deposition method, the physical properties and the main use of hydrogenated amorphous silicon (a-Si:H) layers. The deposition technique commonly used for a-Si:H layers and cells is plasma-enhanced chemical vapour deposition (PE-CVD). The role of broken bonds (or “dangling bonds”) within amorphous layers will be highlighted. Special mention will be made of the Staebler-Wronski effect: the increase of dangling bonds, which act as recombination centres, under the influence of light-exposure. The present main use of a-Si:H layers is in the form of passivation layers within the Heterojunction (HJT) solar cell, which will be described in the next Chap. 7. Section 6.2 will deal with amorphous silicon solar cells. First, the p-i-n structure necessary for amorphous silicon solar cells will be introduced; thereafter, typical characteristics of amorphous silicon solar cells will be given and the advantages and disadvantages of such solar cells listed. It will, thus, become evident, why the amorphous silicon solar cell is the ideal candidate for the generation of electric power in the indoor situation. In Sect. 6.3, our focus will shift to microcrystalline silicon (μc-Si:H) layers. Again, the plasma-assisted deposition technique used for these layers will be discussed. μc-Si:H has been, in the past, mainly propagated for use together with a-Si:H, in a tandem cell configuration; however, with the strong decrease in the price of wafer-based crystalline silicon solar cells, these tandem cells are, at the moment, no longer economically attractive.