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GESEC R&D Inc. Semiconductor Materials Engineering. PREDICTION OF SPACE DEGRADATION OF MULTIJUNCTION SOLAR CELLS. J. C. BOURGOIN, S. MAKHAM & G.C. SUN GESEC R&D, 68 av. de la forêt, 77210 Avon, FRANCE. A – Semi-empirical method. For GaAs:. = 71 / E nl (eV.cm -1 ) , ( in cm -2 ).
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GESEC R&D Inc. Semiconductor Materials Engineering PREDICTION OF SPACE DEGRADATION OF MULTIJUNCTION SOLAR CELLS J. C. BOURGOIN, S. MAKHAM & G.C. SUN GESEC R&D, 68 av. de la forêt, 77210 Avon, FRANCE .
A – Semi-empirical method For GaAs: = 71 /Enl (eV.cm-1) , ( in cm-2)
Experimental verification Using GaAs cell NASA data (proton energies from 0,2 to 9,5keV)*: Standard: the degradation curve of Pm corresponding to 1 MeV electron irradiation. (*) B.E. Anspaugh Solar Cell Radiation Handbook, JPL Pub, (1996).
B – Non empirical method 1-Classical calculation of the current-voltage characteristics of each subcell knowing the minority carrier lifetimes τ of the base and emitter for a given fluence φ: 1/= 1/0 + k k: Introduction rate n & p :Capture cross sections of minority carriers 2- Construction of the degradation of the MJ cell from that of each subcell i: Isc(φ) = minimum (Isci (φ)) Voc (φ) = i (Voci(φ))
Experimental verification Case of a GaInP/GaAs cell (Emcore):
Necessary knowledge, for both base and emitter for each subcell • k, introduction rate (or concentration kφ). • σb, σe, minority capture carrier cross section. • τ0e, τ0b, initial lifetimes. • thicknesses . • Recombination velocities at interfaces. • alloy composition x. Techniques to determine these parameters: • k DLTS, I-V in dark, electroluminescence. • x Low temperature electroluminescence. • τ0e,b I-V under illumination.
