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How Does Solar Cell Output Vary with Incident Light Intensity?

Time Required Short (2-5 days)
Prerequisites None
Material Availability Specialty electronics components required, see Materials list for details
Cost Low ($20 - $50)
Safety No issues


Solar cells are an alternative method for generating electricity directly from sunlight. With this project, you can get down to the atomic level and learn about the world of solid-state electronics as you investigate how solar cells work. Your experiment will measure the effect of changing light intensity on power output from the solar cell. A possible variation would be to investigate the effect of changing the color of the light.


The goal of this experiment is to determine how changes in incoming light intensity affect the output of solar cells.


Andrew Olson, PhD, Science Buddies

Edited by Ben Finio. PhD, Science Buddies


This project is based on:

  • Corlett, N., 2003. "How Does the Intensity of Light Affect Output of Solar Cells?," California State Science Fair Abstract.

Cite This Page

MLA Style

Science Buddies Staff. "How Does Solar Cell Output Vary with Incident Light Intensity?" Science Buddies. Science Buddies, 13 Oct. 2015. Web. 29 Nov. 2015 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Energy_p014.shtml>

APA Style

Science Buddies Staff. (2015, October 13). How Does Solar Cell Output Vary with Incident Light Intensity?. Retrieved November 29, 2015 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Energy_p014.shtml

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Last edit date: 2015-10-13


Solar cells are electronic devices that can transform light energy into an electric current. Solar cells are semiconductor devices, meaning that they have properties that are intermediate between a conductor and an insulator. When light of the right wavelength shines on the semiconductor material of a solar cell, the light creates a flow of electrons. This is known as the photoelectric effect. Small solar cells, like the one used in this project, can be used in circuits to charge batteries, power a calculator, or light an LED (light emitting diode).

In this project, you will measure the open-circuit current and short-circuit voltage produced by a solar cell. How do you think these values will change if you change the brightness of a light bulb used to power the solar cell?

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts:

  • Semiconductor
  • Solar cell (also called photovoltaic cell)
  • Photoelectric effect
  • Light emitting diode (LED)
  • Lumens (unit of light intensity)
  • Voltage (V)
  • Current (I)
  • Resistance (R)
  • Open-circuit voltage
  • Short-circuit current
  • Power


  • How do solar cells turn light into electricity?


This webpage is a good place to start for information on how solar cells work: Watch this NOVA video to learn more information about solar cells and other alternative energy sources: On this page you can build virtual circuits with batteries and resistors, then test your circuit by throwing a switch to light up a bulb. If there's too much current, the virtual light bulb blows up, too little current, and the bulb won't light. When you get the current right, the bulb glows brightly. This page has lots of information about incandescent light bulbs: This webpage has useful information on LEDs:

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Materials and Equipment

Some of the components needed for this project are available from Jameco Electronics:

  • 6 V, 150 mA solar cell with alligator clip leads, part #2221456
  • Digital multimeter, part #2131127
  • clamp-on lamp with reflector, rated for at least 150 W bulbs (available at your local hardware store),
  • At least three light bulbs with different wattages (e.g. 50, 100, and 150 W).
    • Note: the suggested wattages are for incandescent bulbs. If you purchase compact fluorescent (CFL) or light-emitting diode (LED) bulbs, their actual wattages will be lower, but they will display an "equivalent" wattage on the package. While solar panels work best with incandescent bulbs (due to the spectrum of light emitted), for purposes of this science project, you should still be able to use CFL or LED bulbs.

Disclaimer: Science Buddies occasionally provides information (such as part numbers, supplier names, and supplier weblinks) to assist our users in locating specialty items for individual projects. The information is provided solely as a convenience to our users. We do our best to make sure that part numbers and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted or improved, please send us an email if you run across any parts that are no longer available. We also do our best to make sure that any listed supplier provides prompt, courteous service. Science Buddies does participate in affiliate programs with Amazon.comsciencebuddies, Carolina Biological, Jameco Electronics, and AquaPhoenix Education. Proceeds from the affiliate programs help support Science Buddies, a 501(c)(3) public charity. If you have any comments (positive or negative) related to purchases you've made for science fair projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org.

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Experimental Procedure

Note Before Beginning: This science fair project requires you to hook up one or more devices in an electrical circuit. Basic help can be found in the Electronics Primer. However, if you do not have experience in putting together electrical circuits you may find it helpful to have someone who can answer questions and help you troubleshoot if your project is not working. A science teacher or parent may be a good resource. If you need to find another mentor, try to find someone who has hobbies like robotics, electronics, or building and fixing computers. You may also need to work your way up to this project by starting with an electronics project that has a lower level of difficulty.
  1. Set up your experiment as shown in Figure 1.
    1. Connect the multimeter probes to the solar cell's alligator clip leads. If you need help using a multimeter, check out the Science Buddies Multimeter Tutorial.
    2. Set up the lamp a fixed height above the solar cell on a flat surface. The exact distance does not matter as long as you keep it consistent throughout the experiment (for example, 30 cm).
solar cell light intensity
Figure 1. Experimental setup for this project.
  1. Prepare a data table in your lab notebook to record light bulb wattage, brightness in lumens (this information should be available on the light bulb package), open-circuit voltage, and short-circuit current for the solar cell.
  2. Insert your lowest-wattage bulb into the lamp.
  3. Take at least three readings of the open-circuit voltage of the solar cell and record them in your lab notebook.
  4. Take at least three readings of the short-circuit current of the solar cell and record them in your lab notebook.
  5. Insert your next highest-wattage bulb into the lamp and repeat steps 4–5.
  6. Repeat steps 4–5 for each of your remaining bulbs.
  7. Calculate average values for each set of recordings in your data table.
  8. Make two scatter plots, one of open-circuit voltage vs. bulb brightness in lumens, and one of short-circuit current vs. bulb brightness in lumens. How does the solar cell output change as the brightness of the light changes? Does this match your predictions?

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  • This project has you measure open-circuit voltage and short-circuit current, which are the maximum values the solar cell can supply. In reality, which the solar cell is attached to a load, both of those values will drop. Attach the solar cell to a fixed load like a resistor, and repeat the experiment. Calculate the power output of the solar cell (power = current × voltage, or P=IV) under load. How does the power output change with bulb brightness?
  • For more advanced students, can you devise a way to figure out the internal resistance of the solar cell? Is the internal resistance constant, or does it vary with incident light intensity?
  • Test solar cell power output as a function of the angle of the incoming light. Keep the distance and brightness of the light source constant, but vary the angle of the incoming light.
  • Another variation would be to measure the power output of the solar cell as a function of the ambient temperature (see the Science Buddies project A Cool Way to Make Electricity: Solar Cell Power Output vs. Temperature.
  • A more advanced project idea would be to measure the power output of the solar cell as a function of the color of the incoming light. You should do background research to learn how light energy varies with wavelength (color). You will also need to know the spectral (color) characteristics of your light source. For this reason, it would be a good idea to use sunlight for this project. You can get a booklet with 100 color filters for about $10 plus shipping. A search on "color filter booklet" should turn up multiple sources.

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Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

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