Environmental Engineering Reference
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3.0
σ
4.0
σ
2.0
2.0
1.0
ρ
ρ
0.0
0 0.05 0.1 0.15 0.2 0.25
0.0
Iodine concentration in the bath (M)
Figure 4.12 Theimprovementofelectricalconductivity( σ )ofCdTelayers
as a function of I 2 concentration in an electrodeposition bath [35].
In order to test n doping of CdTe, CdS/CdTe device structures
were fabricated using CBD-CdS and ED-CdTe using non-aqueous
electrolytic baths [35]. By growing CdTe at an elevated temperature
of 170 C, layers with larger grains were produced to achieve
high material qualities. The CdTe was doped with varying amounts
of I 2 , and the variation of electrical conductivity (resistivity) was
investigated. Figure 4.12 shows the expected increase in electrical
conductivity, proving the n doping of I 2 in CdTe.
The completed glass/CG/CdS/CdTe/Au devices were charac-
terised using I-V and C-V techniques to study the solar cell
parameters. The I-V curves measured under dark conditions are
showninFig.4.13(a)inthelog-linearscale.Therectificationfactors
as defined by I F / I R at 1.0 V for best devices show over 4 orders of
magnitude. It should be noted that to achieve over 12% e ciencies
from this system, only 3 orders of magnitude rectification factor
is su cient [30]. The barrier heights extracted from the diodes
which show ideality factors less than 1.40 provide φ b values close
to 1.18 eV, which is the most desired Fermi-level pinning position
closest to the valence band maximum. Both the n and the
φ b
 
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