Enhanced Light Absorption in a-Si:H Layers of Solar Cells by Applying Tco/Metal Back Contacts

Abstract

The optimization of the back contact reflectivity for thin film a-Si:H solar cells has been performed. The results of optical calculations show that a-Si:H/TCO/Metal interfaces with a proper TCO thickness reflect much more than their a-Si:H/Metal counterparts. We compared solar cells which were deposited on a flat substrate with different back contacts. The back contacts consisted of a metal layer (aluminum, silver/aluminum) or combined TCO/metal layers (TCO/Al, TCO/Ag/Al). The same was done with solar cells which were deposited on a textured substrate. The solar cells with a TCO/metal back contact showed not only a significantly increased short-circuit current density but also an increase in the spectral response. The cells with TCO/Ag/Al back contact showed the best result.