Solar Energy Solutions

Make Your Home a Solar House with Solar Panels.

How Solar Panels Work.

How Solar Panels Work

Photovoltaic (PV) cells are formed from a wafer of semi-conductor material and although there are now several types in production using different materials, the most common semi-conductor used is silicon.

Pure crystalline silicon is a poor electrical conductor but treat it with tiny quantities of an impurity, either phosphorous or arsenic (a process called “doping”) and enough electrons of these materials are freed to enable a current to pass through. Electrons are negatively charged so this type of silicon is called N-Type.

Dope silicon with gallium or boron and “holes” are created in the crystalline lattice where a silicon electron has nothing to bond with.

These holes can conduct electrical current and the lack of an electron creates a positive charge so this type of silicon is therefore called P-Type. Both types of silicon are modest electrical conductors, hence the name semiconductors.

Put a layer of each kind together in a wafer, such as in a PV cell, and the free electrons in the N side migrate towards the free holes on the P side. This causes a disruption to the electrical neutrality where the holes and electrons mix at the junction of the two layers. Eventually a barrier is formed preventing the electrons from crossing to the P side and an electrical field is formed, separating both sides. This electrical field acts as a diode, allowing electrons to pass from the P side to the N side, but not vice versa.

Expose the cell to light, and the energy from each photon (light particle) hitting the silicon, will liberate an electron and a corresponding hole.

If this happens within range of the electric field’s influence, the electrons will be sent to the N side and the holes to the P one, resulting in yet further disruption of electrical neutrality. Apply an external pathway connecting both sides of the silicon wafer and electrons will flow back to their original P side to unite with the holes sent there by the electric field.

This flow of electrons is a current; the electrical field in the cell causes a voltage and the product of these two is power.

Several factors affect the efficiency of a solar cell. Some cells, mainly ones made from a single material, are only efficient in certain light wavelengths. Single material cells can at the very most expect to convert about 25% of the light hitting it to electrical power.

Research is ongoing into multi-junction cells combining two or more different materials in a single cell. These can have a theoretical efficiency of up to 70% but the cells are problematical in that too many layers can put the crystals under too much strain. The most efficient multi-junction cell so far has attained a 30% efficiency with just two layers.

A recent encouraging discovery has found that alloys of indium gallium nitride have the potential to convert the full light spectrum to electrical power with the added bonus that they could also be very cheap to produce. Types of solar cells