Transcript Solar panels 081211

Solar panels are made up of photovoltaic cells.
A photovoltaic cell converts light energy into electricity.
At the heart of a photovoltaic cell is an NP junction where negative and positive plates made of silicon
and other materials are placed close together. Electrons want to jump across from the Negative to
the Positive side. This force is known as voltage but energy is still needed to make electrons jump
across.
Energy in the form of photons from sunlight enables electrons to jump across which creates the flow
of electricity which is known as current.
Even the best solar cells only achieve around 40% efficiency.
There are several things than can improve the efficiency of solar cells:
Silicon is very shiny so most of the sunlight is reflected which is a waste of energy. This is why solar
panels have a dark non-reflective coating so that more light flows into the cell.
Light can have different amounts of energy just like it can have different colours.
Most solar cells are designed to create electricity with only a small amount of light but this means that
only a low voltage is produced.
The strength of the voltage known as “Band gap energy” depends on how much energy is required
for electrons to jump across the NP junction.
In strong sunlight you get extra current but the voltage doesn’t really increase. New research involves
multi-junction cells which have more than one electric field. This allows the panel to operate in low
light and also take advantage of stronger light with increased current and voltage.
Another issue is that the electricity generated by a photovoltaic cell needs to travel through a
semiconductor and semiconductors aren‘t great at conducting electricity. Wires are good conductors
but they block out light so new transparent conductors are being developed to improve solar cell
efficiency.