Environmental Engineering Reference
In-Depth Information
Table4.2 ThesummaryofI-Vmeasurementscarriedoutbetweendifferentelectricalcontactsmadeonthedevice,asshown
in Fig. 4.11, and the conclusions arising from these measurements. The CG/CdS/CdTe/Au device structures used to perform
this experiment produced conversion e
ciencies of approximately 10%
Two Contacts Measured
Observations
Remarks and Conclusions
1. Measurements between Au and
CG (1and 2) and (1 and 3)
E
ciency is
10%. Rectifying contacts with
reverse current of
∼
There are good solar cells between Au and CG contacts.
∼
10
−
7
A. Series resistance is
∼
100
.
E
ciency is
∼
2. Measurements between twoAu
contacts (2and 3)
0%, and current in both directions
areintheorderof10
−
7
A.
Two Schottky diodes are back to back. Therefore, the current
measured is the reverse current of one of the diodes and there is
no PV activity from this combination.
3. Measurements between In/Ga
and CG (1 and 4) and (1 and 5)
Nil or little PV activity and ohmic currents are
observed with series resistance of
Annealed In/Ga contacts consume p-surface layer and make good
ohmic contacts to the n-CdTe layer. There is no considerable
rectification at n-CdS/n-CdTe interface, and, therefore, PV activity
is minimal.
∼
80
.
4. Measurements between two
In/Ga contacts (4 and 5)
No PV activity and good ohmic currents with
series resistance of
∼
30
are observed.
In/Gamakeohmiccontactston-CdTe,and,therefore,conductionis
throughtheCdTelayer.Thereisnorectifyinginterfacebetweenthe
two contacts.
5. Measurements between Au and
In/Ga (2 and 4) and (3and 5)
E
ciency is
∼
10%. Rectifying contacts with
reverse current
∼
10
−
7
A. Series resistance is
∼
40
.
In/Ga provide ohmic contacts to n-CdTe, and the Au contact pro-
videsrectifyingproperties.Therefore,thiscombinationrepresents
a good solar cell only with the Schottky barrier at the Au/CdTe
interface without theinvolvement of theCdS layer.
