Environmental Engineering Reference
In-Depth Information
Figure 1.14
I-V characteristics of a PV solar cell under dark and
illuminated conditions.
•
Short circuit current density (
J
sc
): This is the current density
produced when the two contacts are short circuited, or when
there is zero voltage across the two contacts. This parameter
is expressed as mAcm
−
2
for convenience and provides easy
comparison between devices fabricated with varying contact
areas.
J
sc
=
I
sc
S
(1.12)
•
Fill factor, or the curve factor (FF): This is a fraction defined to
indicate the shape of the curve or the fraction of electric power
that can be extracted from the solar cell. Therefore, the FF is
defined as
V
m
I
m
V
oc
I
sc
(1.13)
where
V
m
and
I
m
represent the parameters at the maximum
power extraction point (
V
m
,
I
m
).
•
Conversion e
ciency (
η
): After defining the above three
parameters, the light to electric power conversion e
ciency is
defined as
η
=
FF
=
V
oc
·
I
sc
·
Output Power
Input Power
=
V
m
I
m
P
in
=
FF
(1.14)
P
in
