We have previously published the manufacturing process of a copper solar cell for educational purposes. Today we will learn how we can build a Grätzel solar cell for educational purposes.
The Grätzel solar cell is made up of TiO2 (titanium dioxide – semiconductor material) painted with a colorant, an electrolyte (iodine solution), two glass electrodes with a transparent conductive layer (SnO2), and a catalyst (graphite or platen). ).
The manufacturing process is as follows:
1. Preparation of conductive glass plates.
Keep in mind that we are going to work with conductive plates. These glass plates are covered with a conductive film of Sn02, which allows the passage of current. To find out which is the conductive side, we measure the electrical resistance with a multimeter. The conductive side should have a resistance of 20 to 30 Ohms, while the non-conductive side will have infinite resistance (sometimes shown as a “1” on the multimeter). You can buy glass at laboratory supply stores. Just as an example, we put a mark on a collector glass.
Measurement of resistivity of conductive plates.
Secure the sheets to the table with adhesive tape so that you can work with them in the following steps. The driver’s side must be on top.
Preparation of conductive glass plates.
Clean the glass of any traces of grease or handprints using a soft cloth with alcohol. Let it dry.
2. Preparation of the TiO2 solution.
Using a mortar, mix 10 ml of vinegar with 6 g of Titanium dioxide in a smooth and homogeneous way. The solution must be thin enough (like a white paint) to be absorbed by a dropper. To make things easier you can add a drop of liquid detergent or Triton X-100 and let it sit for 15 minutes until the solution dissolves.
Preparation of the Titanium Dioxide solution.
3. Preparation of the negative electrode (-).
With the help of a dropper, deposit the solution on the conductive plate evenly. (You can use a glass plate to help you smooth the mixture.) If the result is not satisfactory, clean the sheet with a damp cloth and repeat the operation. Do not touch the mixture with your hands because you will reduce the efficiency of the cell.
Preparation of the negative electrode.
Using an electric dryer, dry the solution until the wet one has evaporated. Do not bring the dryer too close (maximum about 10 cm from the sample).
Remove the masking tapes being careful not to touch the solution.
Now take the sheet to an oven at a temperature between 450 ° C and 550 ° C for ten minutes. You can also use a Bunsen burner and heat the plate about four inches from the blue flame for about three to five minutes. The white paste will change from white to brown after one minute and then return to color again. Let the sheet cool down.
Sheet drying method.
4. Preparation of the positive (+) electrode.
After determining the conductive side of another conductive sheet and cleaning it, paint it with a number two pencil until it is completely dark. You can also burn the conductive side with a candle.
Preparation of the positive electrode with pencil.
5. Coloring of the negative electrode (-).
We can use a wide variety of dyes to paint our cells: black tea, chicha morada juice, grape juice, beet juice, blackberry juice, etc …
Place the juice in a Petri dish of the appropriate size to immerse the plate with TiO2 with the white side down. Let it sit for about 10 minutes until the TiO2 is no longer white and has the color of the dye.
Examples of colorants that can be used in the solar cell.
Clean the edges of the sheet and then dry them with a blow dryer.
6. Assembly of the solar cell.
Join the two electrodes together using two metal clips. The layer with TiO2 must be in contact with the layer with graphite, but there must be a phase shift between them to be able to place the multimeter contacts later.
This is the assembly of the solar cell.
To activate it, a drop of electrolyte is placed in the cell.
Solar cell activation.
7. Measurement of electric current.
We can test the operation of our cell by connecting it to a multimeter and measuring the electrical current it generates. We can see that the tension will slowly increase.
Now it’s time to test and measure how our solar cell behaves.
Here are some videos to help you with the assembly: