knjiga solarna energija dobra

328 THIN-FILM SILICON SOLAR CELLS
absorption. The amount of the absorption loss depends on the texture parameters, the
thickness of the film, and on the metal itself. The approach for minimizing the reflector
loss in thin amorphous-silicon solar cells is discussed in several papers [60, 61]. Here we
use a similar approach to optimize parameters for the cell structure shown in Figure 8.12.
Figure 8.13(a–d) shows the calculated optical properties of the cells with the basic
structures shown in the inserts of these figures. The MACD and metal loss under different
conditions are also denoted in these figures. In this calculation, the thickness of the cell
considered is 10 µm and the back-contact metal is Al. The texture height is 1.0 micron.
From this figure, it can be seen that as long as either surface is textured, the MACD
of the device will be higher than that of double-side planar cells, even if metal loss is
higher in some cases. Another observation that can be made from these figures is that
the MACD will be improved more (about 30%) in double-sided textured or front-side
textured/backside planar cells. Double-sided textured cells will yield the highest MACD.
This conclusion suggests that double-sided textured or front-side textured structures should
be used in the design of solar cells. The important point is that it is more effective to
R,T,A
1.0
0.8
0.6
0.4
0.2
1.0
Refl.
Total_abs
Metal abs
0.8
Abs_Si
Si
Refl.
0.6
Total_abs
Abs_Si
Metal abs
Al
0.4
MACD = 21.06 mA/cm 2
MACD = 34.33 mA/cm 2
Metal loss = 2.46 mA/cm 2 0.2 Metal loss = 1.50 mA/cm 2
R,T,A
Si
Al
R,T,A
0.0
0.2 0.4 0.6 0.8 1.0 1.2
Wavelength
[µm]
(a)
1.0
0.8
0.6
0.4
0.2
0.0
Refl.
Total_abs
Abs_Si
Metal abs
MACD = 32.15 mA/cm 2
Metal loss = 4.45 mA/cm 2
0.2 0.4 0.6 0.8 1.0 1.2
Wavelength
[µm]
(c)
Si
Al
R,T,A
0.0
0.2 0.4 0.6 0.8 1.0 1.2
Wavelength
[µm]
1.0
0.8
0.6
0.4
0.2
Refl.
Total_abs
Abs_Si
Metal abs
(b)
MACD = 36.64 mA/cm 2
Metal loss = 3.95 mA/cm 2
0.0
0.2 0.4 0.6 0.8 1.0 1.2
Wavelength
[µm]
(d)
Si
Al
Figure 8.13(a–d) Calculated reflectance (R), transmittance (T), and absorbance (A) of a single-junction
cell under different surface configurations. The cell structures are shown in the inset
of the figures. Absorber thickness = 10 µm. (a) Planar, (b) FTBP, (c) FPBT, and (d) DT