Environmental Engineering Reference
In-Depth Information
Table 1
The material costs in the polymer solar cells
Spin casting
($/inch 2 )
Slot/Blade
coating
($/inch 2 )
Slot/Blade
coating
(ITO-free)
($/inch 2 )
Slot/Blade coating
(ITO-free and
evaporation-free)
($/inch 2 )
ITO
0.20
0.20
-
-
Ink (PEDOT,
Active, etc.)
0.060 + 1.200
0.003 + 0.060
0.003 + 0.060
0.003 + 0.060 +
0.002 (Ag ink)
Aluminum
0.104
0.104
0.104
-
Total cost (inch 2 )
1.564
0.367
0.167
0.065
requires expensive vacuum facility. Thus, to meet the requirements of throughput
and material utilization, various practical and efficient coating methods such as
roll-to-roll, blade coating, spray coating, and slot-die coating are being developed
and reported. Here, we give an estimate of the material cost for making OPVs,
which was calculated per inch 2 -area device. Because there is little waste of
solution in the blade/slot coating process, the volume of the solution consumption
is 20-fold less than that of spin coating. For instance, the blade coating having an
ink supplying nozzle utilizes 30 ll solution for a 2 00 9 3 00 size substrate. On the
other hand, spin coating requires more than 500 ll to cover the same area sub-
strate, clearly not suitable for large-scale manufacturing process considering the
high material cost of electronic materials. Another consideration is the ITO
transparent conductor commonly used for organic electronic devices: even though
it has good transparency and high conductivity, its cost has increased significantly
due to the worldwide demand and production of LCD and OLED displays, and
touch panels along with the fact that the indium is a relatively scarce element on
the planet earth. In fact, ITO coated glass accounts for 12 % (spin coating) and
54 % (slot coating) of the whole device cost as shown in Table 1 . Moreover, the
flexible ITO-PET is more expensive than ITO-glass and occupies 35 % in an
electronics device application [ 5 ]. To achieve 1$/W target in the polymer solar
cells, the cost of transparent conductors and the active materials during the process
should be reduced.
1.1 Various Printing/Coating Technologies for Polymer
Electronics
Among conventional printing/coating technologies, the roll-to-roll printing, gra-
vure, flexography, and offset printing offer great productivity compared with other
manufacturing technologies (Table 2 ). However, whether these conventional
printing processes are appropriate for manufacturing polymer electronics should
be considered. For instance, screen printing is a simple printing process but it is
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