Space Solar Cells – 3G30 and Next Generation Radiation Hard Products

Abstract

The 3G30-Advanced, AZUR SPACE's latest qualified solar cell product, provides highest end-of-life efficiencies in space. The cell reaches 27.8% at a fluence of 5 E14 cm -2 and 26.5% at a fluence of 1 E15 cm -2 1 MeV electrons. The cell mass can be reduced to a minimum by substrate thinning, the cell cost can be reduced by implementation of large area configurations and even higher radiation hardness can be achieved by using AZUR's proprietary 3G30-1E16+ design. Various configurations are currently in production. The increasing demand for cells suited for LEO applications, made AZUR to develop a novel upright metamorphic triple junction solar cell with a BOL efficiency of 31% designed for a fluence of 1 E14 cm -2 1 MeV electrons. This cell design is already in production. AZUR's next generation product 4G32 comprises an upright metamorphic 4-junction device with 28.5% EOL (1 E15 cm -2 1 MeV electrons) efficiency. Hence, the 4G32 even surpasses the EOL efficiency of the lattice-matched 3-junction cell 3G30-Advanced. It utilizes the excess current of the Ge subcell by a metamorphic cell concept and a fourth junction added to the stack. This cell will be qualified by mid-2017. This paper summarizes the results and achievements for various 3G and 4G solar cell products from AZUR SPACE, including radiation hardness and cell formats.

Epitaxy for Energy Materials

“…The literature on multiple-junction cells is extremely rich and includes pseudomorphic and metamorphic structures based on III-V multilayers of different compositions deposited on Ge, Si, or GaAs (e.g., [11][12][13][14]). State-of-the-art high-efficiency III-V solar cells use a triple-junction structure that consists of a Ge bottom subcell formed on a Ge substrate, a GaInAs middle subcell, and a GaInP top subcell.…”

Status of Four-Junction Cell Development at Fraunhofer ISE

“…Four-junction cells are being developed as the next generation product for space applications to replace today's triple-junction cells where Ga 0.49 In 0.51 P (1.9 eV) and Ga 0.99 In 0.01 As (1.4 eV) are grown on Ge (0.7 eV) [1][2][3]. The triple-junction cells are well developed and e.g.…”

“…The triple-junction cells are well developed and e.g. the 3G30 product provided by AZUR SPACE reaches 29.5% begin-of-life and 26.5% conversion efficiency under end-of-life conditions (1*10 15 e -/cm 2 1 MeV electron irradiation) [4]. Slightly lower end-of-life results are achieved by Spectrolab [5] and SolAero [6].…”

“…Thus, new cell concepts have evolved where the lattice matching constraint has been dropped. They contain either one or more metamorphic buffer layers where the lattice constant is increased, so that GaInAs junctions with different Indium contents are used as sub-cells [1,3,12]. For example, the upright metamorphic four-junction solar cell architecture developed by AZUR SPACE (4G32) is introduced to space qualification by the end of 2016 [1].…”

“…They contain either one or more metamorphic buffer layers where the lattice constant is increased, so that GaInAs junctions with different Indium contents are used as sub-cells [1,3,12]. For example, the upright metamorphic four-junction solar cell architecture developed by AZUR SPACE (4G32) is introduced to space qualification by the end of 2016 [1]. This cell architecture is an evolutionary development of an upright metamorphic triple-junction cell previously developed at Fraunhofer ISE for terrestrial concentrator applications [13].…”