Goldsmiths’ 2013

Build your own solar cell

Aim: To make and test a solar cell using a common product as the dye

In order to do this experiment properly you do need to get some specialist materials. You can buy a whole kit or buy the parts separately. You also need a beaker big enough to soak the glass plate in juice, a petri dish, tissues, a pencil, latex gloves, two bulldog clips, two crocodile clips, two leads and a multimeter.

http://www.mansolar.nl/supplies.html

http://www.mansolar.nl/products.html

1. Choose your natural dye

In pairs, choose which food or drink you’d like to try and figure out how to get the best coloured liquid from your material (if you are using whole fruit you will need to find a way to extract the juice).

Write down which material you chose here ………………………………………….

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2. Stain conducting layer with dye

Stain the white conductive side of the glass plate which has been previously coated with titanium dioxide (TiO2). A multimeter can be used to check which side of the glass is conductive. Soak the film for 5 – 10 minutes until it gets a deep colour. Wash the plate with water and blot gently with some tissue.

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3. Coat the counter electrode

The solar cell needs both a positive and a negative plate to function. The positive electrode is called the counter electrode. Use a pencil lead to apply a thin graphite (catalytic carbon) layer to the conductive side of plate’s surface. This acts as a catalyst in the reaction to regenerate the dye molecules.

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4. Add the electrolyte

The Iodide solution serves as the electrolyte in the solar cell to complete the circuit and regenerate the dye. Place the stained plate on the table so that the film side is up and place ONE drop of the iodide/iodine electrolyte solution (toxic – wear gloves) on the stained part of the film.

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5. Assemble the cell

Place the counter electrode on top of the stained film so that the pencil coated side is touching the film. Offset the glass plates so that the edges of each plate are exposed. These will serve as the contact points for the negative and positive electrodes so that you can extract electricity and test your cell. Use two clips to hold your cell together. (You might have to ask for help with this bit)

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Test your cell using the multimeter!

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Above pictures show the solar cell circuit being connected together.

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Above left is the current for the orange juice and on the right is the pd for the orange juice.

Below left is David Stanton (PhD student) seeing whether light intensity makes any difference to the current and pd readings. Below right are some of the readings for the different fruits chosen.

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Above left is David Stanton (PhD student) seeing whether light intensity makes any difference to the current and pd readings. Above right are some of the readings for the different fruits chosen.

You can work out the power of you cell by measuring the Current and Voltage and using the formula below.

Your Current = ……………………..

Your Voltage = ………………………

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Extra activity

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The chosen liquid was poured into a curvette. A cuvette is a small tube of circular or square cross section, sealed at one end, made of plastic, glass, or fused quartz (for UV light) and designed to hold samples for spectroscopic experiments.

The curvette was put into a colorimeter in order to measure the peak absorbance wavelength. This would be the wavelength which the solar cell would have the maximum efficiency.

http://en.wikipedia.org/wiki/Cuvette

A colorimeter is a device used in colorimetry. In scientific fields the word generally refers to the device that measures the absorbance of particular wavelengths of light by a specific solution. This device is most commonly used to determine the concentration of a known solute in a given solution by the application of the Beer-Lambert law, which states that the concentration of a solute is proportional to the absorbance.

http://en.wikipedia.org/wiki/Colorimeter_(chemistry)

http://en.wikipedia.org/wiki/Colorimetry_(chemical_method)

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The above left photograph shows Dr Stephen Flower (organiser of the course at the University of Bath) carrying out the colorimetry experiment (it is computer controlled). The above right shows the result for the orange juice. The left side of the graph is due to absorbance of the container. You can just make out two absorbance peaks (456.96nm on the left and 487.83 on the right). The reason why the peaks aren’t very prominent was because we should have diluted the juice.

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