How Solar Cells Work

Free Green Electricity A solar cell can convert light into electricity. This is particularly beneficial if the light is free as in daylight? Given the costs and environmental consequences of fuels such as oil, gas and coal used in generating electricity, isn’t it nice that solar cells can give us energy for free & without releasing greenhouse gases?

Electrical energy and electric circuits Electrical energy from a mains socket this comes from power stations over a grid of wires that spans the country some wires are underground, but some you can see on pylons Electrical energy from a battery this comes from a chemical reaction in the battery when the chemicals are all used up the battery dies

Electrical energy and solar cells Electrical energy from a solar cell in a solar cell light energy from the Sun is converted into electrical energy the more light energy striking the solar cell the more electrical energy will be generated

Electric currents electrons An electric current is due to the flow of billions upon billions upon billions of tiny particles called electrons. Electrons flow from a region of low (or negative) voltage to one with a higher (or positive) voltage (this can be created by a battery).

Electrons Meet an electron. It is part of a vast family where everyone looks identical. Each electron is a tiny particle that causes electricity. Electrons are found in every material. Like most family members electrons need their own space and repel other family members if they get too close.

Electrons and conductors and insulators In an electrical conductor electrons are free to move about easily. Metals are electrical conductors. In an electrical insulator electrons are not able to move about easily. Materials such as plastics, rubber and glass are common electrical insulators.

Electrons and semiconductors Some electrons live in materials called semiconductors. A semiconductor is a funny material where some electrons may have enough energy to travel about freely, but only if they are warm enough, or in a bright light. As its name suggests, a semiconductor has properties in between those of an electrical conductor and an electrical insulator.

Electrons and semiconductors When two semiconductors are joined together, they can form a step. For the electrons to flow around the circuit they must gain energy to jump from the lower level up on to the step. A solar cell can be made from two semiconductors joined in this way.

Solar cells In a bright enough light, the electrons are lifted by the light energy and given enough energy to jump up the step. When they jump up the step, they generate a voltage difference that allows them to then travel back though an external circuit. This forms an electric current which supplies energy to a load such as a lamp or motor just like a battery. With no light, the electrons cannot jump up the step, there is then no current and no energy is transferred around the circuit.

Using solar cells Solar cells can be of various sizes and used to provide energy that can be stored in rechargeable batteries, or used directly, to power lights, fans, road signs, calculators, homes and even whole towns. They are, however, rather costly and inefficient: further research and development should solve these problems.

Summary A solar cell converts light energy to electrical energy. A solar cell is like a battery but powered by light instead of a chemical reaction. A solar cell is made from semiconductor materials. Shining light on to the solar cell causes electrons in the solar cell to gain electrical energy. When there is a complete conducting circuit the electrons which have gained electrical energy can flow around the circuit transferring their energy to some form of load such as a lamp or a motor.