Scientists in Brazil have developed an instrument that lets researchers examine a solar cell while it is generating electricity.
A synchrotron instrument can examine a working solar cell from the insideThe development addresses a problem in photovoltaic research.
Testing whether a solar cell produces electricity does not necessarily explain what is happening inside its materials.
Heating a solar cell can also cause its supporting materials to expand, potentially moving the sample away from the measurement position.
Advertisement AdvertisementThe new system accommodates an entire solar cell on a specially designed holder.
Scientists in Brazil have developed an instrument that lets researchers examine a solar cell while it is generating electricity. The system uses powerful X-rays to investigate what happens inside a complete working device, rather than requiring researchers to remove individual materials and study them separately.
Developed at the Brazilian Center for Research in Energy and Materials (CNPEM), the equipment operates at the Sirius synchrotron facility. It combines nanoscale X-ray imaging with controlled temperature, illumination, humidity, and electrical conditions. Researchers can therefore investigate how a solar cell's internal structure changes while it performs the job it was designed to do.
A synchrotron instrument can examine a working solar cell from the inside
The development addresses a problem in photovoltaic research. Testing whether a solar cell produces electricity does not necessarily explain what is happening inside its materials. Conventional measurements can reveal changes in electrical performance, but they cannot always identify the microscopic processes responsible.
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Researchers can fire focused X-rays at the device while it is operating and get information on its chemical make-up and crystal structure. This can be useful, as in many cases removing or taking apart the device for examination can alter the very conditions researchers are trying to understand.
The initial work is on perovskite solar cells. These photovoltaic devices have attracted research interest, but understanding their behavior and long-term stability remains important. Their internal structure can respond to temperature and environmental conditions, making observations during operation particularly useful.
The instrument is installed at the CARNAÚBA X-ray nanoprobe beamline at Sirius, Brazil's synchrotron light source. A synchrotron generates exceptionally bright X-rays that can be focused on very small regions. Here, researchers use these beams to examine areas of a working device at a scale that ordinary electrical testing cannot reach.
Keeping the cell steady while changing its environment
Examining a sample with a focused X-ray beam creates a mechanical challenge. The beam is extremely small, so even the slightest movement can shift the area being examined. Heating a solar cell can also cause its supporting materials to expand, potentially moving the sample away from the measurement position.
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The new system accommodates an entire solar cell on a specially designed holder. It is designed using grade 5 titanium alloy, and it can accommodate differences in thermal expansion thanks to its flexible mounting elements.
The team tested the custom holder by repeatedly changing its temperature between 30 and 150 degrees Celsius. Measurements continued over approximately 20 hours, with each temperature held for an hour. As the temperature rose from 30 to 150 degrees Celsius, the sample shifted vertically by approximately 5 micrometers.
Horizontal displacement was approximately 1 micrometer. The displacement proved reversible when the temperature returned to its starting point.
Temperature is only one variable the equipment can control. The holder also supports illumination, electrical bias, and atmospheric control, including humidity and gas composition management. This allows researchers to recreate several conditions a photovoltaic device might encounter without removing it from the measurement setup.
X-rays reveal changes that ordinary performance tests cannot explain
The researchers demonstrated these capabilities on a complete perovskite solar cell. Their X-ray diffraction measurements identified individual perovskite grains approximately 2 micrometers across. They also mapped the distribution of lead and iodine within the device.
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A temperature experiment provided another example. The crystal structure was first mapped at 40 degrees Celsius and then again at 65 degrees Celsius. The crystal lattice parameter increased with the temperature. This gives researchers a direct way of looking at the structural changes rather than just going by the changes in the electrical output.
The platform could help researchers investigate why a solar cell loses efficiency or how particular conditions affect its materials. It is now available as a multi-user research facility, although some capabilities, including X-ray beam-induced current measurements, are still being implemented. For photovoltaic research, the important advance is the ability to connect what happens inside a working cell with the electricity it produces.
Sources: Agência FAPESP, American Chemical Society, Tech Xplore
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