Page 103 - Mirjam-Theelen-Degradation-of-CIGS-solar-cells
P. 103
Experimental information
R s J
+
J ph J d R sh V
J sh
Figure 3.8
Single diode model: equivalent circuit of a non-ideal solar cell showing the impact of series and shunt resistances.
resistance, represents the resistance encountered by the current flowing in the solar
cell. The major part of this resistance is due to the resistivity of the front and the back
contact. The other resistive effect is R , which is the shunt or parallel resistance. This
sh
parameter describes how easily the current can cross the pn-junction instead of
flowing in the external circuit. When these resistances are included in the circuit, we
obtain the single diode model (Figure 3.8), in which the voltage and current are linked
by equation (3.5) [4]:
qVRJ− s VRJ
()
−
JJJe=− +−1 + s (3.5)
nkT
ph
0
R sh
In order to show the impact of the resistances as well as other recombination effects,
the fill factor (FF) is derived from current voltage curves. The fill facor is the ratio of
the maximum output power to the product of J and V and is a measure of the
OC
SC
´squareness´ of the J-V curve.
×
VJ
FF = MPPMPP (3.6)
oc ×
VJ
sc
Finally, the efficiency is the ratio between the maximum output power and the
incident power:
××IFF
×
VI
η === V (3.7)
P MPP
MPPMPP
oc
sc
P incident P incident P incident
where η is the efficiency and P incident is the incident power of the illumination, which is
2
often taken as 1000 W/m .
In this study, the efficiency (η), short circuit current density (J), open circuit voltage
sc
101
R s J
+
J ph J d R sh V
J sh
Figure 3.8
Single diode model: equivalent circuit of a non-ideal solar cell showing the impact of series and shunt resistances.
resistance, represents the resistance encountered by the current flowing in the solar
cell. The major part of this resistance is due to the resistivity of the front and the back
contact. The other resistive effect is R , which is the shunt or parallel resistance. This
sh
parameter describes how easily the current can cross the pn-junction instead of
flowing in the external circuit. When these resistances are included in the circuit, we
obtain the single diode model (Figure 3.8), in which the voltage and current are linked
by equation (3.5) [4]:
qVRJ− s VRJ
()
−
JJJe=− +−1 + s (3.5)
nkT
ph
0
R sh
In order to show the impact of the resistances as well as other recombination effects,
the fill factor (FF) is derived from current voltage curves. The fill facor is the ratio of
the maximum output power to the product of J and V and is a measure of the
OC
SC
´squareness´ of the J-V curve.
×
VJ
FF = MPPMPP (3.6)
oc ×
VJ
sc
Finally, the efficiency is the ratio between the maximum output power and the
incident power:
××IFF
×
VI
η === V (3.7)
P MPP
MPPMPP
oc
sc
P incident P incident P incident
where η is the efficiency and P incident is the incident power of the illumination, which is
2
often taken as 1000 W/m .
In this study, the efficiency (η), short circuit current density (J), open circuit voltage
sc
101
