Ingenieur Vol. 75 ingenieur July 2018-FA | Page 23

Incoming photon
T h e m e c h ani s m o f P V
electron has been
electron
Hole
left
after
the
Freed
ejected
phenomena is best explained
Incoming photon
electron has been
electron
using fundamental physics.
ejected
Electron in
The fusion of p-type and n-type
outer shell
semiconductors results in the
Electron in
Before
After collision the silicon atom has a net
formation of a p-n depletion region
outer
shell collision between the photon
with the electron
positive charge and has lost one of its
that ends up with an inverted Before collision between the photon
After collision
the silicon atom has a net
electrons.
positive charge and has lost one of its
built-in potential. As light quanta with the electron
electrons.
Figure 4.
Photoelectric Effect process.
of adequate energy impinge this
region, electron-hole pairs are
Figure
4. Photoelectric
Effect process.
Figure
4: Photoelectric
Effect process.
produced. These are swept by the built-in electric
field into the respective sides of the region. When
Sunlight
Direction of electric
an external conducting path is connected across
field
Sunlight
the opposing sides of the p-n device, electricity
Direction of electric
field
flows, thus powering up any device along its path.
Metallic
All of these are elegantly explained using the
grid
Back metal
Photoelectric Effect, for which Albert Einstein was Metallic
contact
grid
Back metal
awarded a Nobel Prize in Physics.
Flow of
p contact
type
electrons
n type
The PV cell is the smallest unit and several
Flow of
p type of movement of
Direction
cells are connected in series-parallel to make up electrons
n type
free
electrons
Ammeter
a PV module. The modules are arranged in series
Direction of movement of
to form a string whilst strings are combined in Ammeter
free electrons
Electrical load
A
parallel to form an array. The present state of PV
Electrical load
A
module conversion technology is listed in Table 1.
Figure 5: Completing the loop.
Figure 5. Completing the loop.
Figure 5. Completing the loop.
Table 1: Efficiency of Solar Cells in 2017
(Source https://onlinelibrary.wiley.com/doi/epdf/10.1002/pip.2978)
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