Spectroscopic ellipsometric analysis of silicon-rich silicon nitride layers for PV applications

Silicon-rich silicon nitride (SRN) layers are of great interest for the 3^rd generation solar cells. They can be used as luminescent converters to enhance photovoltaic (PV) conversion in the blue spectrum or, as high band-gap materials in an all Si tandem cells. Silicon nanoparticules (Si-nps) of controlled size and density embedded in the silicon nitride (SiN) matrix as a light converter film are investigated for the first application. For the tandem cell application, a superlattice composed of nano-sized SiN layers containing Si-nps is used. The aim of this work is to use spectroscopic ellipsometry to study the optical (band gap) and structural (size, density) properties of Si-nps embedded in SRN layers. The extracted size and bandgap of Si-nps from SE modeling were verified with high resolution TEM and room temperature photoluminescence (PL).