Optical and electrical properties of SiGe/Si solar cell heterostructures: Ellipsometric study

SiGe thin films with different Ge fraction were obtained by Molecular Beam Epitaxy (MBE) on silicon (001) substrates. The SiGe thin films properties are obtained using Spectroscopic Ellipsometry (SE) in the frame of the New Amorphous model. This model demonstrates that depending on the Ge fraction high absorption coefficients of order 106 cm−1 were obtained. The solar cell performance of SiGe/Si heterostructures was measured using a JASCO YQ-250BX system with light source of AM 1.5 solar simulator. The experimental results obtained (y = 0.15, Wa-Si: H = 2 nm) yielded to an improvement of about 1.3 mA cm−2 for the short-circuit current density, and about 2.2% for the cell efficiency compared to the conventional cell i.e. without a-Si:H thin layer (FSF).