The Impact of Ultraviolet Radiation in High Temperature Space Missions

IR

Search this article

Description

Concentrated ultraviolet (UV) radiation in combination with high temperature was found to constitute an aggressive environment for standard space photovoltaic assemblies. A high intensity, high temperature (HIHT) environment, typical for missions to the inner planets of the solar system like Mercury, characterized by temperatures of 500 K and 11 solar constant irradiance in the UV region below 400 nm, was simulated in vacuum. Independently of the triple junction cell technology used, module degradation up to 20 % in maximum power was observed during several hundred hours of test. Electroluminescence analysis identified discrete top cell shunts close to the cell edge, in particular around the front side contact pads. Cross-sectional transmission electron microscopy performed on several degraded cells revealed an etched contact pad metallization / cap layer interface and more importantly, several 100 nm large, oriented Cu3P inclusions at the shunted locations. A chemical degradation mechanism is proposed. Short wavelength UV light interacting with polysiloxanes used asmodule encapsulant produces hydrogen and methyl radicals. With these building blocks an organic acid can be formed on external reaction surfaces like the Ag busbars that simultaneously serve as a source of oxygen. Cu traces present in the Ag segregate to the surface and are transported by this acid to the contact pad of the cell in the liquid phase. This UV induced degradation mechanism is also able to explain the distinctly non-equilibrium surface morphology found on Ag surfaces after HIHT exposure: Ag particles of different aspect ratios, 50-1000 nm in size, including a small fraction of nanorods, had formed on the surface.

形態: カラー図版あり

Physical characteristics: Original contains color illustrations

資料番号: AA0061889006

レポート番号: JAXA-SP-12-008E

Journal

Keywords

Details 詳細情報について

Report a problem

Back to top