Comprehensive Study of Performance of Silicon Heterojunction Solar Cells Under Electron Irradiation

With their low price, availability in large volumes and increasing performances, the re-assessment of the potential of modern silicon-based solar cell technologies for space applications becomes more and more relevant. Among these technologies, silicon Heterojunction solar cells processed from Ga-doped wafers hold the record efficiency among all p-type based single junction devices, with 26.6% recently demonstrated. Such a high efficiency potential, combined with a p-type base doping (expected to confer better radiation hardnesses) and the compatibility of the Heterojunction technology with very thin wafers, make such cells particularly promising for space applications. In this work, a comprehensive experimental plan, spanning various wafer thicknesses, resistivity values and characterization techniques, was implemented to probe the electron radiation hardness of Ga-doped silicon Heterojunction solar cells and precursors. The work presented here focuses more precisely on the dependence on the fluence of end-of-life IV performances of cells made from wafers with resistivity values up to
$60\ \Omega.\text{cm}$
. EQE measurement is used to confirm the trends observed under sun simulator for the short-circuit current and explore the wavelength dependence of the electronic degradations. Based on these results, guidelines for optimum thicknesses, resistivity values and material parameters for these Si solar cells are discussed.