New 3C Silicon Carbide on Silicon Hetero-Junction Solar Cells for UV Collection enhancement
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New 3C Silicon Carbide on Silicon Hetero-Junction Solar Cells for UV Collection enhancement M. Toureb, B. Berenguiera L. Ottaviania, M. Pasquinellia, O. Palaisa, P. Di Lauro a, M. Portailc, S Chenotc, T. Wooda, D. Koborb a
IM2NP (UMR CNRS 7334) – Université Aix-Marseille, Case 231 - 13397 Marseille Cedex 20, France b Laboratoire de Chimie et de Physique des Matériaux (LCPM), UFR Sciences et Technologies, Université Assane Seck de Ziguinchor, BP 523, Ziguinchor, Sénégal c CRHEA (Research Center on Hetero-Epitaxy and Applications) Nice, France. E-mail: [email protected], [email protected] ABSTRACT An actual trend to enhance solar cells efficiency is to build multijunction cells, creating a bandshape wavelength collection. However, the best multijuction cells are actually made of III-V compounds when silicon and its alloys don’t lead to high efficiency devices. In this article, we study a 3C-SiC/Si heterojunction as a first step for 3C-SiC/Si tandem cells. Four samples were fabricated by depositing 3C-SiC on Si wafers with different SiC doping levels. Simulations of the structures are performed, as well as optical and electrical characterizations of the heterojunction cells.
INTRODUCTION Among the permanents efforts to enhance photovoltaic cells efficiency, an actual trend is to build a band shape wavelength collection also called multi-junctions solar cells, where several single junctions made of different materials with different bandgaps are stacked, each one collecting a part of the spectra. Thus, III-V compounds are currently dominating the multi-junction field, with a 40.7% efficiency world record for a GaInP/GaInAs/Ge triple junction cell, and four or five junctions cells should be realized soon [1]. However, Silicon and its alloys are still a field of interest for producing multi-junction cells. High development degree of silicon technology, lower cost of fabrication and non-toxicity are good arguments to follow this way. In case of tandem cell, the optimal bandgap for the top junction would be between 1.6 and 1.8eV, but few materials compatible with silicon are presently available meeting this requirement. The use of a-Si for the top cell on crystalline Si presently leads to 23% efficiency [2]. 3C silicon carbide (3C-SiC), with 2.36 eV bandgap could be a potential replacement material. SiC is known for his ability to resist to high radiation level, making it suitable to work in solar concentrators. 3C-SiC/Si heterojunctions have already been studied in the domain of power diodes, as window layer or as emitter for photovoltaic cells in several configurations [3][2][4]. The opportunity to make 3C-SiC/Si tandem cells has been studied theoretically [5][6], leading to a theoretical efficiency of 26%, but at our knowledge, this type of cells has not been realized yet. The first step in order to realize 3C-SiC/Si tandem cells is to masterize the deposition of 3C-SiC on Si wafers. This work is a preliminary study of 3C-SiC/Si heterojunctions, produced at the CRHEA (Research Center on Hetero-Epitaxy and
