How do solar cells work?

Question

How do solar cells work?

Answer 1

When light hits the solar panel, it pushes electricity through the solar panel.  Electricity can only go through the panel one way, so it flows back through your wire.

Answer 2

Photoelectric solar cells rely on semiconductors in order to produce electricity.

To understand how semiconductors are used in solar panels you need to know some things about Chemistry.  Atoms contain protons, neutrons, and of course electrons.  The number of electrons depends on the element.  Hydrogen has 1 electron.  Silicon happens to has 14 electrons but only 4 of those are free to be shared with other atoms.  This is what makes silicon special it can share it's 4 free electrons with 4 more silicon atoms and those share with other silicon atoms and so on and so on.  This creates a crystal structure much like a square box with each corner as an atom

http://en.wikipedia.org/wiki/Silicon#Pur...

Semiconductors in general, use this same basic structure to function as they do.  In the solar application Photons from the sun enter the cell and when one strikes an electron it gives that electron enough energy to break free of the bond being shared by two atoms.  This electron then moves across the crystals searching for a new hole to fill within the crystal structure.  The more pure the semiconductor the further the electron has to go before it finds a new space to fill.  Movement of electrons is called electric current.  

The current is generated by placing areas of semiconductor with holes already in the material and areas with implanted atoms with extra electrons.  The way these areas are constructed causes the electrons to flow in one direction, allowing you to connect a + and - terminal.  Any electrons that reach the terminals are what you see as the electricity that you use.

3 of the major problems with solar panels are...

1.As the solar panel ages the holes in the semi conductor slowly will become filled and the efficiency will become less and less. ( as with all semi-conductors ) All materials try to reach equilibrium.

2.Solar efficiency depends on how much of the suns power can be captured and transferred into electricity.  Much of the suns power reflected back out the same way it entered the cells.  Other amounts of the energy are wasted when the photons collide with something other than an electron and create heat.  As the entire cell heats up electrical efficiency decreases and material properties break down.  Current technology only gives around 40% power return at PEAK performance which is very rare during real world applications.

3. The third downside is that it actually costs More energy to refine and produce the semiconductors required to build a solar panel ( The temperature required for carbothermal reduction of silica is in the range of 2100–2300 °C) than the solar panel will ever recover from the sun in it's entire lifetime.  And since you cannot repair a damaged panel, prolonged life through maintenence is minimal.

Answer 3

There are a few versions of solar cells

Gallium Arsenide, Silicon (several versions of silicon) and a newer one Dyesol

http://www.sandia.gov/pv/docs/PVFSCGalli...

http://www.howstuffworks.com/solar-cell....

http://www.dyesol.com/index.php?page=How...

Basically the simplified version.

Photons of light are absorbed by a material this causes either an electrical or chemical reaction which results in a flow of electrons.

There is about 1 kilowatt of energy that reaches every Square metre (3.28x3.28 feet) of ground in the form of sunlight.

It has been a couple of years since I played around with solar powered cars but at that stage it was possible to buy cells that where just over 30% efficient. (I.E. about 300 watts/ sqr metre). A company called Emcore supplied them (at a price). These high end cells are intended for satelite use. (triple layered Gallium arsenide)

These very expensive cells are used on high end solar powered race cars.

Example http://en.wikipedia.org/wiki/Nuna

For most purposes silicon is prefered as it is significantly cheaper to produce power , but requires about twice the area.

Solar panels are regularly guarenteed for 25 years and will produce power for much longer.