Science Buddies: "Ask an Expert"

This previous year, I did my science project on the effect of different light-colors on the efficiency of a silicon solar cell. For my project next year, I would like to try testing the band-gap of a material on the efficiency of a solar cell using three solar cells, one made from an insulator, a semiconductor, and a conductor. However, such solar cells are not readily available to the public. I was wondering if you could suggest a way to make a simple model of solar cell from scratch, so I can change the materials that they are made from and test my hypothesis.

Thank you!
Kelsey Levine

candy4me - I understand your project last year evaluating the various wavelengths of light and their energy generating capability in a silicon PV cell. I'm not aware of any ability of a strictly insulating or conductive material to be sensitive to photon conversion to energy. Perhaps I am misunderstanding your hypothesis, but the concept of 'band-gap' seems totally related to a semiconductor P-N junction. Can you give me more information on your research and perhaps I can be of more assistance.

Rick Marz

Hello candy4me,

I think Rick Marz is right that solar cells are only made from semiconductors but not insulators or metals. Some people are experimenting with solar cells of a completely different type using plastic materials or even living cells.
Another problem for building your own is that the semiconductor cells are made using many very expensive machines that I'll guess you don't have at home. A practical experiment for an individual would be to buy solar cells made from different semiconductor types and geometries and compare the efficiencies, wavelength responses and other properties. You could try to explain the differences based on the construction of each one.

Good luck, WW

Thank you for your replies.

I would really like to test if a multijunction solar cell will perform better than a silicon solar cell. I have a silicon cell, but that is only solar cell that is really available - you can't get other types of individual cells unless buying them to power your home. So I wondered if you had suggestions for a way to test the efficiencies of different solar-cells. My first thought was simply to make a model of a solar cell from scratch, but, like you said, actual solar cells are expensive and difficult to manufacture.

candy4me - You are just nibbling along the edge of a fascinating science - solar energy. The amount of solar energy reaching the earth is measured in Exajoules/unit of time. This number is about 5.5 million Exajoules/year. While that amount isn't easy to appreciate, consider that it is about 7,000 times the total amount of energy currently being consumed on earth. In fact, the amount of energy from the sun that reaches the earths atmosphere is almost 1,400 watts per square meter. That says, a very small percentage of solar energy, when effectively converted and stored, could greatly reduce our current dependency on fossil fuels like oil and coal. I didn't mean to digress from your question, but it may suggest you explore the bigger picture in your research on solar cells and their potential effect on future society.

With regards silicon solar cells, I don't exactly understand your reference to multi-junction solar cells with regards solar cells in general. Most large solar cell panels are made up of arrays of individual pieces of silicon (although we mostly talk about silicon, other exotic semiconductor materials can also be used) that contain a single P-N junction. This is especially true of cells constructed of polysilicon or single crystal silicon. That is because there are limits to the size the silicon ingot can be drawn from it's "melt". There is another manufacturing process that is known as "thin-film" where the P-doped and N-doped materials are evaporated onto an insulating substrate, often a plastic film, to create a solar cell. These can be produced in a continuous process that yields very large area solar materials. There are many sources you can search on the internet to delve further into this subject.

Rick Marz

candy4me wrote:This previous year, I did my science project on the effect of different light-colors on the efficiency of a silicon solar panel. For my project next year, I would like to try testing the band-gap of a material on the efficiency of a solar cell using three solar cells, one made from an insulator, a semiconductor, and a conductor. However, such solar cells are not readily available to the public. I was wondering if you could suggest a way to make a simple model of solar cell from scratch, so I can change the materials that they are made from and test my hypothesis.

Thank you!
Kelsey Levine

It is top project have you completed it? For my college final assignment I have chosen similar project so please help me with your true experience.. Waiting for reply thanks in advance:)