Silicon-based solar cells Characteristics and production processes ...

Silicon-based solar cells – characteristics and production processes
The numerical matching of the I-V characteristics with a single or double diode
model makes it possible to calculate directly the value of the photocurrent, the
voltage, the dark current, as well as the parallel and series resistance of the cell [59].
Fig. 26. Scheme of the equivalent electrical circuit in a double diode model for an actual
silicon solar cell; designation in accordance with the dependence (20).
The mathematical model which most thoroughly describes the non-linear I-V
characteristics of a solar cell is the equation (20) with seven parameters, which one
can obtain by applying Kirchhoff’s Law to the equivalent circuit presented in Fig. 26
[60].
( V IR ) ⎞ ⎤ ⎡ ⎛ q( V+
IR )
⎡ ⎛ q +
⎤
s
s
⎞ ⎛ V+
IR
s
⎞
I = I ⎢
⎜
⎟ − ⎥ − ⎢
⎜
⎟ − ⎥ −
⎜
⎟
ph
− IS1
exp
1 IS 2
exp
1
(20)
⎣ ⎝ A1kT
⎠ ⎦ ⎣ ⎝ A
2kT
⎠ ⎦ ⎝ R
sh ⎠
or
⎛ V+
IR ⎞
s
I = Iph
− I1−
I 2 −
⎜
⎟
(21)
⎝ R
sh ⎠
and
I 1 = I
where:
I
( V IR )
⎡ ⎛ q +
⎢exp
⎜
⎣ ⎝ A1kT
⎞ ⎤
⎟ −1⎥
⎠ ⎦
s
S 1
, 2
( )
⎡ ⎛ q V+
IR ⎤
I =
s
⎞
I ⎢exp
⎜
⎟ − 1⎥
(22a) , (22b)
S 2
⎣ ⎝ A
2kT
⎠ ⎦
- current possible to obtain from the solar cell
I - photocurrent generated by electromagnetic radiation
ph
I
1
- dark diffusion current
I
2
- dark generation-recombination current
I S1 - saturation current of dark current diffusion component
I S2 - saturation current of dark current generation-recombination component
V - voltage possible to obtain from the solar cell
R s - cell’s series resistance
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