Environmental Engineering Reference
In-Depth Information
Figure 3.1
A schematic diagram showing the main features of a simple
electrolytic cell used for the electrodeposition of semiconductors.
(
1 mA), is applied across the lab-scale-size anode and
a cathode, the positive ions are attracted to the cathode, electrically
discharged, and chemically reacted to form the material CuInGaSe
2
.
The working electrode (cathode) is usually an electrically conduct-
ing surface, and in the solar cell development, glass/conducting
glass is a convenient substrate. The material properties depend on
a number of parameters, such as ionic concentrations, electrodes
used, the pH value, the stirring rate, the temperature, the nature of
the substrate, the deposition voltage and the time. The optimisation
of these parameters allows growers to produce semiconducting
layerswiththedesiredstructural,mechanical,electronicandoptical
properties. Aqueous solutions enable growth temperatures varying
fromroomtemperatureupto
∼
85
◦
C,andothernon-aqueousmedia
such as ethyleneglycol and dimethylsulfoxide (DMSO) allow an
increaseintemperatureupto
∼
170
◦
C.Theinitialcurrent-voltage(I-
V)curveoftheelectrolyte,orthevoltammogram,helpsinestimating
the approximate growth voltages of different phases of materials.
With this information, growth voltages can be optimised to produce
layers with desired properties. The material layers grown by
electrodepositionareusuallyamorphous,nano-ormicrocrystalline,
and therefore this method is a convenient technique for the growth
∼
2Vand
∼
