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photvoltaic cell

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Introduction Solar Cells are used to convert available light into electrical energy. They do this without the use of chemical reactions. This conversion process is based on the work done by a French physicist named Alexander Becquerel in 1839. He discovered the photoelectric effect, which describes the release of positive and negative charge carriers in a solid state when light hits its surface. He found, when experimenting with an electrolytic cell made up of two metal electrodes, that some materials would produce small amounts of current when exposed to light. Fifty years later a scientist named Charles Fritts created the first real solar cell using junctions by coating the semiconductor with a nearly transparent layer of gold. A semiconductor is a material such as silicon or germanium, where the material has properties which fall between conductors and insulators. However the efficiency of this conversion of light to electricity was less than 1 percent. Next in 1930 a semiconductor was made using copper oxide, yet the efficiency of the conversion was still less than 1 percent. This was overcome in 1954 when silicon was used for the semiconductor and the efficiency was increased to 6 percent. Then by 1989 the use of a device, which concentrated light onto the cell surface using a lens, increased the efficiency to 37 percent. ...read more.


This means that the photons from the lamp could not get through to the surface of the cell. Therefore the semi-conductor inside the cell could not get hit by all the photons and this intern means that the electrons could not get excited to create a strong voltage. When the whole of the cell was covered there was still voltage, this means that the black paper that I used to cover the cell was letting some of the photons of light through. This shows that the paper was not thick enough, so the results that I recorded weren't accurate. The experiment was rough so didn't need to be that accurate but the results that I did get did show a definite trend. The experiment: For my experiment I will measure the voltage that comes out of the photovoltaic cell at different heights when a fixed light source id shone onto it. Variables: When investigating a solar cell, there are several variables we could investigate. Below, I have analysed all the variables that could be investigated, and evaluated which one I will investigate. Variable 1: Light Light can have different colours, and different coloured lights are known to have different frequencies. This in turn would cause the different coloured lights to emit different levels of power. ...read more.


* 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 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. A way in which I will make my results more reliable is by placing black paper to act as a boarder around my experiment. This will ensure that no other surrounding light will affect my results. Safety: When conducting an experiment we must always consider safety. The safety of the experimenter and other people around you. When doing my experiment I will have to be careful that the lamp does not get too hot and that I don't burn my self on the lamp. I will also have to be careful when cutting the black paper with the scissors. Accuracy: For this experiment I will be using a voltmeter to record the voltage, the voltmeter has its own limitations in that it only goes to two decimal places so the percentage error will be +/- 0.005. When dealing with the small voltages that the cell will out put this percentage error could come into play. I will improve the accuracy by enclosing my experiment in a box lined with black paper. This will absorb any residual light. ...read more.

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