In-Depth Analysis of III-V/Epi-SiGe Tandem Solar Cell Performance Including Advanced Light Trapping Schemes
Abstract
The growing interest in new concepts of III-V/Si tandem solar cells arises from the need to reduce the cost of high efficiency
III-V based multi-junctions by using low cost substrates such as silicon. Because it is still a challenge to grow III-V materials directly
onto Si wafers due to thermal expansion and lattice mismatch issues, other ways of combining III-V compounds and Si have been
developed. Among them is the reversed metamorphic concept recently proposed by Cariou et al.. In the latter approach, the Si bottom
cell is deposited by low temperature PECVD (<200°C) directly on the III-V top-cell, preventing the degradation of the electrical
properties of the underlying III-V layers grown by MOVPE. Though the possibility to obtain a high crystalline quality for the epitaxial
silicon or silicon-germanium alloys has already been demonstrated by the same authors, precise evaluations of both the electrical
properties of the epi-Si absorber and the overall performance of such a tandem cell are mandatory. For this purpose, in this work we
propose an in-depth electrical and optical analysis of the potential of this concept in terms of efficiency by means of simulations and
characterization.