gesec r&d inc. semiconductor materials engineering prediction of space degradation of...
TRANSCRIPT
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 .
p
e
p=
e
electron (1 MeV )
proton(EP)P
m
Voc
Isc
Log fluence
A – Semi-empirical method
= 71 /Enl (eV.cm-1) , ( in cm-2)
For GaAs:
Experimental verification
Standard: the degradation curve of Pm corresponding to 1 MeV electron irradiation.
Using GaAs cell NASA data (proton energies from 0,2 to 9,5keV)*:
(*) B.E. Anspaugh Solar Cell Radiation Handbook, JPL Pub, (1996).
104 105 106
10-13
10-12
10-11
10-10
10-9
p-1 (
cm2 )
Enl (eV.cm-1)
108 1010 1012 1014 1016
0,4
0,6
0,8
1,0
No
rmal
ized
Max
imu
m p
ow
er
Particle Fluence (cm-2)
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 + kk: 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))
Case of a GaInP/GaAs cell (Emcore):
Experimental verification
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.
Prediction of degradation (2J Emcore)
0,00 0,03 0,06 0,09 0,12 0,15
0
10
20
k (
102 c
m-1)
Enl (107 eV/cm)
Determination of k versus energy