Development of Wider Bandgap n-type a-SiOx:H and mu c-SiOx:H as Both Doped and Intermediate Reflecting Layer for a-Si:H/a-Si1-xGex:H Tandem Solar Cells

Abstract

In this work, we developed a-SiOx:H(n) and mu c-SiOx:H(n) films as n-type layer, intermediate reflecting layer (IRL), and back-reflecting layer (BRL) to improve the light management in silicon thin-film solar cells. In the development of SiOx:H films, by properly adjusting the oxygen content of the films, the optical bandgap of x-SiOx:H(n) can be increased while maintaining sufficient conductivity. Similar effect was found for a-SiOx:H(n). In a-Si:H single junction cells, employing a-SiOx:H(n) as the replacement for a-Si:H(n) resulted in a relative efficiency enhancement of 11.4% due to the reduced parasitic absorption loss. We have also found that pc-SiOx:H(n) can replace back ITO layer as BRL, leading to a relative efficiency gain of 7.6%. For a-Si:H/a-Sil..,Ge.,:H tandem cell, employing pf-SiOx:H(n) as IRL increased the current density of top cell. In addition, employing a-SiOx:H(n) as a replacement of a-Si:H(n) in the top cell increased the current density of bottom cell due to the reduction of absorption loss. Combining all the improvements, the a-Si:H/a-Si1-xGex:H tandem cell with efficiency of 9.2%, V-oc = 1.58 V, J(SC) = 8.43 mA/cm(2), and FF = 68.4% was obtained.