Environmental Engineering Reference
In-Depth Information
defect compound layer also has an n-type electrical conduction
and a bandgap of
∼
1.30 eV. Therefore, several research groups
have proposed a possibility of the formation of a hetero-junction
between the p-CIGS and n-ODC layers. This concept has also not
been experimentally or otherwise confirmed to date, but the idea
is floating around in the research community. But the observations
of Fig. 5.2 show that the natural ordered defect compound (ODC)
layer with n-type electrical property sets well within this energy
band diagram between p-CIGS and n-CdS layers. Such layers with
ordered defects at interfaces in electronic devices could produce
defectlevelswithhighconcentrationsandcouldfirmlypintheFermi
level in these structures. This will be discussed in later sections of
this chapter.
5.5 Reported Device Performance
Thedevicestructuredescribedaboveremainsthesamefordifferent
research groups, but material production processes and layer
thicknesses used have slight differences. As a result, the device
performanceshowsawidevariation,makingitdi
culttorecognise
any specific patterns. In order to identify systematic patterns, it
is important to consider only results reported for best performing
devices. Table 5.1 summarises the results reported for solar cells
showing e
ciencies greater than
∼
12%.
Table5.1 Asummaryofopencircuitvoltagevaluesreportedbydifferent
research groups for devices showing e
ciencies in excess of
∼
12%
Reference
V
oc
Values Reported (V)
Identified Group
M. A. Contreras
et al.
[1]
(0.42-0.55),
∼
0.65,
∼
0.75, (0.80-0.90)
A B C D
S. Ishizuka
et al.
[30]
∼
0
.
70
C
D. Rudmann
et al.
[31]
(0.60-0.68)
B
D. Ohashi
et al.
[32]
(0.48-0.52),
∼
0.62
A B
T. Nakada
et al.
[33]
∼
0
.
53
A
Y. Nagoya
et al.
[34]
∼
0
.
55
A
O. Lundberg
et al.
[35]
∼
0
.
65
B
∼
.
T. Nakada
et al.
[36]
0
60
B
