knjiga solarna energija dobra

330 THIN-FILM SILICON SOLAR CELLS
R,A
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Si
Al
5 µm
Reflectance
Absorption in metal
Absorption in Si
5 µm
15 µm
15 µm
5 µm
15 µm
0.4 0.6 0.8 1.0 1.2
Wavelength
[µm]
Figure 8.15 Calculated values of reflectance, Si absorbance, and metal absorbance for two
cells, 5 µm and 15 µm thick, showing mechanisms of the enhanced absorption. The cells have
front-polished and back-textured configuration. Texture height was 1.0 µm
MACD
[mA/cm 2 ]
40
38
36
34
32
30
28
26
24
22
20
18
16
14
(a)
(b)
(c)
Front textured/back textured
Front textured/back polished
Front polished/back textured
Experimental data from Kaneka
0 5 10 15 20
Cell thickness
[µm]
Si
Al
Si
Al
Si
Al
Figure 8.16 Calculated maximum photocurrent generated in a cell with light-trapping involving
a metal reflector
the film thickness has reached about 10 µm. Furthermore, texturing at both interfaces
appears to be the most suitable cell configuration. Figure 8.16 includes experimental data
from Kaneka [45, 46]; the solid points show excellent agreement with calculated results.
One can deduce the effect of light-trapping by comparing J SC values in Figures 8.1 and
8.3 for the same thickness of the cell. In Figure 8.1, the thickness required to generate
a J SC of 34 mA/cm 2 is 80 µm. However, the structures of Figure 8.16 can produce the
same values of J SC for a thickness of about 10 µm – a factor of 8 thinner.