JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Radiation Resistance of InGaP/GaAs Dual-Junction
Thin-Film Space Solar Cell
M. Imaizumi a) , S. Sato b) , T. Ohshima b) , M. Takahashi a) and K. Kibe a)
a) Institute of Aerospace Technology, JAXA,
b) Environment and Industrial Materials Research Division, QuBS, JAEA
Increasingly, solar panels are being required to have less
weight and volume, namely, higher specific power in W/kg
and lower stowage volume in W/m 3 . There are two ways
to meet these requirements. One is to improve the solar
cell efficiency, and the other is to reduce the weight and/or
thickness of solar cells. However, if a thin-film III-V
multi-junction solar cell can be achieved, it realizes both
properties of high-efficiency and lightweight. We have
developed an InGaP/GaAs thin-film dual-junction (TF2J)
solar cell 1), 2) . In this paper, we present comparison of the
radiation resistance of the TF2J cell and conventional 3J
cells 3), 4) .
A hundred of the TF2J cells were prepared for proton
irradiation experiment. No laminating film was applied on
the front surface of the cell. The initial efficiency of the
cells was in the range of 20-23% under AM0, 1sun
(136.7 mW/cm 2 ) at 25 °C. Also, a conventional
InGaP/GaAs/Ge triple-junction (3J) space solar cell was
prepared for comparison. The thicknesses of the InGaP
and GaAs sub-cells in the TF2J and the 3J cells are
equivalent.
The cells were subjected to proton irradiation at the
following energies; 100 keV, 200 keV, 380 keV, 1 MeV,
3 MeV, and 6 MeV with varied fluences. The
current-voltage (I-V) output characteristics and the external
quantum efficiency (EQE) of the cells before and after
irradiation were measured. The results of the TF2J cell
were compared with those of the 3J cell.
The remaining factors of the short-circuit current (Isc),
the open-circuit voltage (Voc) and the maximum power
(Pmax) of the TF2J and the space 3J cells irradiated with
various energies of protons are compared in Fig. 1. The
fluence of all energies of protons is equal (1 × 10 12 cm -2 ).
In the energy range of 200 - 400 keV, radiation resistance of
the TF2J cell is superior to that of the 3J cell. Protons in
this energy range stop in the GaAs sub-cells according to
TRIM simulation 3) . Therefore, the energy range is the
4)
most destructive to space 3J cells . In the case of
380 keV-proton irradiation, the value of Isc of the TF2J cell
after the irradiation is significantly higher than that of the 3J
cell. In addition, the Voc values of the two types of cell
irradiated are almost equivalent although the TF2J cell has
dual-junction structure. These facts result in higher Pmax
value for the TF2J cell after the irradiation.
Typical degradation in EQE of InGaP and GaAs
sub-cells in the TF2J cell and the 3J cell before and after the
380 keV-proton irradiation were compared. It reveals that
the better radiation resistance of Isc of the TF2J cell is
JAEA-Review 2010-065
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Remaining Factor
Remaining Factor
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
Isc
Voc
Pmax
0.01 0.1 1 10
Proton Energy (MeV)
Isc
Voc
Pmax
(a) TF2J cell
0.01 0.1 1 10
Proton Energy (MeV)
(b) #502 3J cell
Fig. 1 Dependency of remaining factors of Isc, Voc and
Pmax of (a) TF2J cell and (b) #502 3J cell on
irradiated proton energy. The fluence of each energy
proton is 1 × 10 12 cm -2 .
attributed to higher radiation resistance of the GaAs sub-cell
in the TF2J cell.
From these results, the TF2J cell is thought to require less
radiation-shielding materials such as coverglass or other
laminating films than conventional 3J cells. This is a great
advantage for developing lightweight and flexible solar
panels.
References
1) T. Takamoto et al., Proc. 31st IEEE Photovoltaic
Specialists Conf. (2005) 519-524.
2) T. Takamoto et al., Proc. 4th World Conf. of
Photovoltaic Energy Conversion (2006) 1769-1772.
3) M. Imaizumi et al., Proc. 29th IEEE Photovoltaic
Specialists Conf. (2002) 990-993.
4) T. Sumita et al., Proc. World Conf. of Photovoltaic
Energy Conversion (2003) CD 3P-B5-10.