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Measuring Solar Cells with a Source Measure Unit

Source measure units are vital pieces of equipment used for many applications, including the measurement of new solar cells.

A small-scale test device is usually used to characterize the solar cell efficiency. These devices are too small to generate usable power but allow you to test the design. Exposing the cell to a known amount of light power, using a solar simulator, allows you to calculate the electrical power produced per unit area. Power is simply voltage multiplied by current:

Equation to calculate electrical power of a solar cell. Power equals voltage times current
Equation to calculate electrical power

Individual Measurements

A starting point is to measure the applied voltage across the solar cell and the current produced per unit area. You can measure the voltage generated by placing a multimeter across the terminals while the cell is illuminated. Similarly, you can measure the current using a multimeter, and divide this by the area of the solar cell, to calculate the current density.

If you measure current density and voltage individually, this only tells you how much power per unit area a perfect solar cell device generates. This is because a good voltmeter has a very high internal resistance, and a good ammeter has near zero internal resistance:

  • When measuring voltage by itself, no current can flow and hence no power is generated.
  • When measuring the current across the terminals, the device is being tested when it has been short-circuited.

Simultaneous Measurements

For a real solar cell, the voltage output will depend on how much current is produced. A source measure unit is able to vary the voltage and measure the change in current simultaneously, giving you a more accurate depiction of how a solar cell will behave in the real world.

Source Measure Unit

  • Affordable and Accurate
  • Five Current Ranges
  • Dual Channels

£1,450 With Free Shipping

Solar Cell JV Curve

A J-V curve, also referred to as an I-V curve, shows how the voltage and current are affected by one another, and allows you to calculate the amount of power that a solar cell generates. Below is a typical JV curve for a working solar cell. Understanding how to interpret J-V curves is incredibly useful when troubleshooting problems with your solar cell.

Graph plotting a JV curve for a prototype perovskite solar cell
Typical J-V curve for a prototype perovskite solar cell

If you multiply the voltage by the current density, you get the power density produced by the solar cell. The peak of the graph below is the point at which maximum power is generated.

When performing these measurements, you should always measure the solar cell when a negative voltage has been applied, known as reverse bias. This indicates a good quality device.

Reverse bias also reveals whether there is any extra current available that you are not using effectively. Applying a negative voltage can extract additional charges from the device. While these charges do not generate power, they allow you to understand some of the photocurrent loss mechanisms.

Graph plotting the power density produced by a pervoskite solar cell
Power density produced by a perovskite solar cell

Measuring J-V curves is an important tool in solar cell development and optimization, which is made easy with the Ossila Source Measure Unit. And in combination with our push-fit electrical test boards, you can quickly and accurately test devices in a range of standard sizes. Along with the Ossila Solar Simulator, we have created a solar cell testing kit containing everything you need to test your solar cell devices.

Contributing Authors

Reviewed and edited by

Dr. Mary O'Kane

Application Scientist

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