Physics Case Study Solar Electric Panels

Figure 1. Diagram to show photoelectric effect

How charges create electricity

Semiconductors that form solar panels can be doped with acceptor or donor impurities which creates more positive holes or more free electrons and are called p-type and n-type semiconductors respectively. Within a solar panel, p-type and n-type semiconductors are placed next to each other. Initially, the electrons in the n-type semiconductor and positive holes in the p-type semiconductor diffuse and create charged regions known as the ‘space charge region’.  When they reach this point, it leaves behind a negatively charged area at the p-type side, and a positively charged area at the n-type side. As there is a negative and positive region, it creates an electric field. This electric field, opposes the diffusion of electrons and positive holes, creating a potential difference. The electric field allows electrons to move from the p-type semiconductor to the n-type semiconductor, creating a diode. The component comprising of the two semiconductors is called an n-p junction.

Figure 2. Diagram to show n-p junction

How light creates electricity

When a photon of light creates an electron-hole pair on the n-type semiconductor, and it moves to the space charge region, the electron will diffuse to the p-type semiconductor. By creating an external link from the p-type to the n-type semiconductors, the electric field will move the electron back to the n-type side to join back with the positive hole. The energy the electric field exerted to move the electron from the p-type side to the n-type side is the work done, and the movement of the charge is a current.

Implications to society

By harnessing the sun’s energy, it provides people with a free and renewable energy source. Since the Earth receives enough energy in 1 minute from the sun to power human needs for a year, it is important to use some of this powerful energy source. The modern solar cell was designed in the 1950s which found practical uses in the first satellites and now is used for general electricity production and mass production. There is a growing need for solar energy despite its inefficiency, due to issues regarding global warming and fossil fuel consumption. The problems with solar cells are their inefficiency and cost as opposed to fossil fuels. People must be willing to pay more for solar energy as opposed to fossil fuel energy. This is being resolved by the on-going research on improving efficiency and reducing costs on the production of solar cells.

Practical investigation

I will be investigating the internal resistance of a solar cell to theoretically predict the maximum power output of the solar cell. By finding the internal resistance, I can match the internal resistance with the resistance of the external load for maximum power output. By doing so, I can theoretically find the efficiency of the solar cell.

By Jonathan Gee

Bibliography

• Edexcel AS Physics Students’ Book
• Wikipedia - , ,
• Howstuffworks -
• My teacher – The Boswells School