Reflection Suppression in a GaAs0.77P0.23/Si Tandem Step-Cell

• DOI: 10.4229/eupvsec20152015-1bv.7.37
• Publication Date: 2015-11-03
• Authors: Dahlem; Eugene A. Fitzgerald; Ammar Nayfeh; Sabina Abdul Hadi; Tim Milakovich; Sueda Saylan
• Keywords: Reflection; Tandem

31st European Photovoltaic Solar Energy Conference and Exhibition; 241-244<br/>In this paper, we investigate the reflection suppression in a GaAs0.77P0.23/Si tandem step-cell through antireflection coatings (ARCs). We evaluate the different designs by computing the solar weighted reflectance (SWR), using the transfer matrix method (TMM). Various material combinations are investigated, and the performance of double-layer and triple-layer ARC designs are presented. All the investigated double-layer designs minimize the reflectance above wavelengths of 450 nm. The best antireflection performance is obtained for designs that also minimize reflection down to wavelengths of 400 nm, which occurs for the SiO2/TiO2 stack (SWR = 1.99% between 300-725 nm). The triple-layer designs further decrease the reflectance, mainly at shorter wavelengths, when compared to their double-layer counterparts. The best antireflection performance is obtained with a triple-layer design based on a MgF2/Si3N4/TiO2 stack (SWR= 1.51%). In addition, both MgF2/HfO2/TiO2 (SWR = 1.61%) and SiO2/Si3N4/TiO2 (SWR = 1.73%) stacks show similar performance. Our analysis indicates that a step-cell incorporating an optimized ARC offers about 56% improvement in the JSC of the top subcell, compared to a cell without ARC (17.8 mA/cm2 vs. 11.4 mA/cm2).<br/>