How does a solar cell produce electricity? (Solar Energy Course 2020 Part 5 of 12)


How does a solar cell produce electricity? Find out in this video. This video is part of iPolytek’s online course
on solar energy. iPolytek, Professional Development Courses
for Engineers. A PV system works on the principle of converting
sunlight directly into electricity through the use of solar cells in combination with
several other basic components. The solar cell is the building block of a
PV system. Several solar cells are connected together to form a module. Several solar
modules are connected together to make up a solar panel. And finally, many solar panels are connected
together form a solar array. PV systems also include cabling, monitoring,
tracking, and protection equipment as shown in the diagram. Inverters are used to convert
the direct current produced by the solar modules to the alternating current required by most
of the electrical equipment used in residential, commercial and industrial applications. Batteries
can be used to store electricity for later use. Let’s take a closer look at the primary building
block of a PV system, the solar cell. The solar cell is made of semiconducting material,
such as silicon that has been “doped” with an agent that has the propensity to either
gain or lose electrons, such as phosphorus or boron. Silicon that has been doped with phosphorus
can lose electrons and is known as an N-type semiconductor. This is because phosphorus
has 5 valence electrons as compared to silicon’s 4.
Since an N-type semiconductor wants to lose electrons, it acquires a positive charge. Conversely, silicon that has been doped with
boron has a shortage of electrons, or an abundance of “holes”, and is known as a P-type semiconductor.
This is because boron has 3 valance electrons as opposed to silicon’s 4. So P-type silicon
wants to lose holes and gain electrons, and as a result, acquires a negative charge. When these two types of silicon are joined
together they form a PN junction. This is the foundation of the
solar cell. When the P and N zones are brought into contact
the surplus holes and electrons from each side recombine, creating ions. This depletes
the holes and electrons in that region, hence the term “Depletion Region”. A voltage barrier
forms in this zone. Eventually, only ions are found in this region. They create an internal electric field (E)
at the junction. The force of the electric field acts in the
opposite direction to the diffusion force and prevents the remaining free charges in
each zone to cross the junction to recombine. When a photon hits a solar cell, one of three
things can happen The photon can pass straight through the cell.
This happens to low energy photons. The photon can be reflected by the surface
of the solar cell. Or the photon can be absorbed the silicon
to create electricity. This is known as the photovoltaic effect. Now we know the basic structure of the solar
cell but that’s just half the story. To really understand how solar cells produce electricity,
we have to move on to the question: What is the photovoltaic effect? Find out in our next video! See you soon and
thanks for watching.

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