Environmental Engineering Reference
In-Depth Information
of an organic insulator, this layer prevents the in- and out-diffusion
of metal and semiconductor elements. This layer also prevents
chemical reactions between the two inorganic materials, the metal
and the semiconductor. This leads to an increase in the device
lifetime, removing ageing effects at the electrical contact. This is an
ideal way to improve performance, stability, and lifetime of PV solar
cells by fabricating hybrid-devices combining inorganic and organic
materials.
In the place of an insulating layer, a p-type conducting polymer
can be used. In this case, the intermediate layer can have large
thicknesses, which will be an advantage in producing organic-
inorganichybriddevices.
1.5 Characteristics of a Solar Cell
As described in the above sections, a typical PV cell contains one
or more interfaces producing rectifying property and two electrical
contacts on both sides to collect charge carriers. The nature of
the two electrical contacts can vary according to the device design
used, with generally used ohmic contacts. However, metal contacts
with rectifying properties can also be used to enhance the existing
electric field within the device, as described in later chapters of this
topic. The following section uses a simple solar cell device structure
based on a rectifying Schottky diode to illustrate the characteristics
of a solar cell and its conversion e
ciency. Details of other PV solar
cell devices are well documented in previous publications [16-20].
1.5.1
I-V Characteristics of a Solar Cell Under Dark
Conditions
Figure 1.10 shows a schematic diagram and the corresponding
energy band diagram of a simple solar cell based on a rectifying
Schottky contact formed on an n-type semiconductor. The front
contact can be fabricated using a transparent electrical contact
or grid type contact to minimise the effect of shading. The
back electrical contact is a usual ohmic contact to collect charge
carriers.
