Environmental Engineering Reference
In-Depth Information
In the scientific literature, there are many occasions when high
J
sc
values have been experimentally observed and reported, but the
PV community has been reluctant to accept these values over the
past few decades. On one hand there is a claim that PV e
ciencies
could reach values over 60% [1, 2, 3], and on the other hand
experimentally observed high
J
sc
values exceeding 40 mAcm
-
2
,
cannot be accepted by the same community. There seems to be
a confusion here in the scientific thought process and this needs
radical changes in the way we look at and understand the PV
process.
Atthispointitisworthreconsideringthebasicexpressionforthe
solar energy conversione
ciency given by the following equation:
V
oc
.
FF
.
J
sc
P
in
Inordertoachievehighe
ciencies,thethreeparameters,
V
oc
,fill
factor (FF), and
J
sc
, should bemaximised.
η
=
•
V
oc
values are now almost approaching the bandgap of the
semiconducting material used. For example, GaAs (
E
g
=
1.43 eV) produces
V
oc
values of 1.175 V. Therefore
V
oc
values are almost saturating and expected e
ciencies
above 60% cannot be realised through this parameter.
•
FFvalueshaveachievedmid-80%,andthesearethehighest
possible values that can be reached for this parameter.
Therefore, there is no room for further improvements of
conversion e
ciency arising from the FF values.
•
Then, any anticipated improvements in e
ciency must
arise from
J
sc
. If we are to double the present-day
e
ciency,
J
sc
should be doubled. The current average
value of
J
sc
30 mAcm
-
2
must be doubled to about 60
mAcm
-
2
in order to double our existing e
ciencies. It
is high time we think differently for the benefit of PV
developments
∼
The following is a short communication to the author by a well-
respected scientist in the PV field.
