knjiga solarna energija dobra

VERY HIGH EFFICIENCY CONCEPTS 147
70
Efficiency h
[%]
e g
65 1.11 1.23 1.34
1.46
0.98
1.56
60
1.66
Tandem (series connected)
55 1.44 1.50 1.57
1.76
1.63
1.40
1.71
1.79
1.87
50
45
40
Single gap
35
30
T a = 300 K
1.87
1.95
25
0.5
0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
Energy e 1
[eV]
Figure 4.15 Limiting efficiency for the IB solar cell under maximum concentrated sunlight. For
comparison, the limiting efficiency of single-gap solar cells (in this case, ε l ≡ ε g ) and a tandem
of two cells that are series-connected are also shown (in this case, ε l labels the lowest band gap
of the cells and the figures on the curve correspond to the highest of the band gaps). (Reproduced
from Increasing the Efficiency of Ideal Solar Cells by Photon Induced Transitions at Intermediate
Levels, Luque A. and Martí A., Physical Review Letters V. 78 N. 34, 5014–5017, by permission
of American Physical Society © 1997)
Barrier semiconductor
Contact
Contact
p
n
Quantum
dots
Conduction band
Fermi
level, E F IB
0.71 eV
1.24 eV
Valence band
Figure 4.16
IB formation in QD arrays