A solar cell is a device for converting solar energy into electricity. High performance solar cells, which you can buy at Radio Shack and other stores, are made from specially treated silicon and require huge factories, high temperatures, special cleaning and a lot of money.
If we want to sacrifice efficiency for the ability to make our own solar panels in the kitchen using materials from a hardware store, we can demonstrate a working solar battery in about an hour.
Our solar cell is made of copper oxide instead of silicon. Copper oxide is one of the first materials in which scientists discovered the photoelectric effect, in which light causes electricity to flow through the material.
Thoughts on how to explain the photoelectric effect is what led Albert Einstein to the Nobel Prize in physics and the theory of relativity.
1.Copper sheet from the hardware store. It usually costs about 150 rubles. for 0.9 square meters. We need about 45 sq. cm.
2. Two clips "crocodile".
3. A sensitive microammeter, which can measure gaps between 10 and 50 microamperes. Radio Shack sells small multimeters with a LCD MONITOR. But you can also use a regular one.
4. Electric oven. My kitchen stove is a gas stove, so I bought a small electric stove with one helix for about 750 rubles. The small 700-watt burners probably won't work - you need at least 1100 watts to turn the burner red.
5. Plastic bottle with a cut neck. I used a 2 liter bottle of mineral water.
6. Table salt. We will need a couple of tablespoons.
7. Water from the tap.
8. Sandpaper or drill with such a nozzle (abrasive)
9. Sheet metal.
Here is the burner.
First you need to cut off some of the copper so that it is the size of an electric stove. Wash your hands to avoid greasy or other stains.Also wash the copper sheet with detergent to wash away grease or other stains from it. Use sandpaper or an abrasive brush to completely remove the copper sheeting so that any sulfide or other light corrosion is removed.
Then put a blank copper sheet on the tile (electric) and turn it on to the maximum.
Copper will begin to heat and oxidize , you will see beautiful red-orange spots on its surface.
When copper heats up even more, multi-colored spots will be replaced with black copper oxide color.
All colors This disappears when the spiral is already red.
When the burner burns, the copper sheet will be covered with black copper oxide. Allow it to fry for another half hour, so the black coating will be thick. This is important because the thick coating will peel off easily, while the thin coating will remain sticking to the copper.
After half an hour of cooking, turn off the burner.Leave the hot copper on the burner to cool slowly. If you cool it too quickly, the black oxide film will stick to copper.
As the copper cools, it shrinks. Black copper oxide also shrinks. But they are compressed at different speeds, which causes black copper oxide to peel off.
Large pieces will fall off soon, it's fun to watch))
>div style="text-align: left;">When the copper has cooled to room temperature (this takes about 20 minutes), most of the black oxide film will go away. Easy cleansing with your hands under running water will remove most of the small pieces. DO NOT ATTEMPT to tear off resistant stains and do not bend the sheet - you may damage a thin layer of copper oxide, but we need it
The rest of the assembly is very fast and simple.
Cut the second sheet of copper to fit the size of the first (heated). CAREFULLY bend the two pieces so that they enter the plastic bottle without touching each other.
Attach "crocodiles" to both plates.Connect the wire from pure copper to plus and the wire from the plate with oxide to the minus.
Now mix a couple of tablespoons of salt in a small amount of hot tap water. Stir until all the salt has dissolved. Carefully pour the mixture into the bottle (where the plates are), leaving about 2.5 cm from the edges of the plates.
In the photo above is a ready-made solar battery. In the shade, the ammeter shows approximately 6 milliamperes. But even in the dark this The battery will give several milliamps))
This photo shows the battery in the light, and the ammeter shows 34 miles, sometimes the battery can give and 50 miles EP, or even more.
How does it work?
Copper oxide is a semiconductor. It is an intermediate conductor, where electricity can flow freely, and an insulator, where electrons are strongly connected to their atoms and do not flow freely.
There is a gap in a semiconductor, called the band gap between electrons that are strongly associated with an atom, and electrons that are farther from an atom that can move freely and conduct electricity. .
Electrons cannot stay in the band gap.An electron can give only a little energy and move from the nucleus of an atom to the forbidden zone. The electron must receive enough energy to move further from the nucleus, outside the forbidden zone. Similarly, an electron outside the forbidden zone can not lose a little energy and fall just a little closer to the core. This should lose enough energy to fall past the forbidden zone into an area where electrons can be. When sunlight hits electrons in copper oxide, some of the electrons get enough energy from sunlight to jump past the bandgap and become free to conduct electricity.