An Investigation into the Factors, which affect the Voltage Output of a Solar Cell

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Hayley Gardner

An Investigation into the Factors, which affect the Voltage Output of a Solar Cell

My aim is to try and find out how much the voltage is affected when exposing different sized areas of a solar cell to a light source. From this I will also establish the energy of each photon and approximately, the number of freed electrons, which can make an electric current flow.

I know that light consists of packets or quanta of energy called photons. When electromagnetic radiation such as light shines on materials (usually metals), which emit electrons the light photons containing energy are captured by the electrons. This means that the electron absorbs the energy from a photon thus allowing it to escape from the surface of its material. For each light photon landing on the surface of a material which emits electrons, an electron can be ‘free’.  

I know that solar cells contain thin wafers of silicon protected by glass. When light photons strike the surface of the solar cell, energy from the photon is absorbed by an electron. The electron needs a certain minimum energy to escape the material but excess energy or surplus energy is transferred to the electron as kinetic energy. Thus creating an electric force, this pushes the electrons around a circuit, known as an electric current, when the solar cell is connected up. The size of the voltage depends on the number of flowing or ‘freed’ electrons.

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From looking at the methodology of my preliminary experiment I know that there are many other variables. In my preliminary experiment my main aim was to investigate as many other variables as I could think of, which might affect the output or voltage. I did this because by considering all the other variables I am able to regulate them, keeping my experiment as fair as possible. The other variables or independent variables that I have noted from my preliminary investigation include:

  • Keeping the light source (lamp or ray box) the same distance from the solar cell through out all experiments that I carry out. I will place the solar cell 15cm away from the light filament. I will establish this distance by ensuring that my light source contains a transparent bulb.
  • Keeping the colour of my light source the same. From my knowledge of the photoelectric effect I know that the shorter the wavelength of light, the higher the energy of photon. Therefore a photon of ultraviolet for example which has an extremely short wavelength will have about twice as much energy of a infrared photon of light which has a very long wavelength. I will use white light in my investigation.
  • Keeping the solar cell at the same angle to the light source through out the experiment.
  • Keeping the light emission by the light source the same. I will not alter the electrical input to the light source. As some of the output energy is emitted as light photons.

I know that the formula for calculating electrical power is P = IV or

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            power = voltage x current.

From my preliminary experiment I have also taken in to account other ways in which to make my results more reliable and easier to record. They are placing a white piece of paper under the solar cell and the light box and drawing around them. This enables me to see exactly where my apparatus are situated therefore allowing me to keep the distance between them the same. Another way in which I will make my results more reliable is by placing black paper to act as a ...

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