Environmental Engineering Reference
In-Depth Information
Figure 6.1
Theapproximateshapeofthesolarspectrumandarrangement
of three different p-i-n diodes to absorb photons in three regions. The
bandgap within one cell is constant, but the materials in cell-1 have larger
bandgaps than those in cell-3.
increasingtheshortcircuitcurrentdensity.Theapproachistofabri-
cate p-n, p-i-n, or any other diode structure with different bandgap
semiconductors and connect them to enhance the PV conversion.
As shown in Fig. 6.1, cell-1, at the front, is fabricated with a wide
bandgap material to convert high-energy photons from the blue-
end, while cell-3, at the back, is fabricated with a narrow bandgap
material to convert low-energy photons from the infrared (IR) end.
In this tandem solar cell approach, the next step is to connect
the cells together to form one tandem solar cell device. There are
two possible ways of achieving such a tandem solar cell — either by
connecting them in series or in parallel configuration.
6.2.1
Connection in Series
This typeofconnectioniswidely usedtoday byconnectingadjacent
devices in series using a tunnel junction. A schematic diagram of
