By Andrew Venzie
The KU Physical Sciences Department has students every year who are blessed with the opportunity to conduct research alongside their professors. Since this past summer, a research project regarding silicon solar cells has been in the works in the Physics Department. Carlos Sosa, Andrew Venzie, Taylor Worthington, Amanda Portoff and Austin Zimmerman are conducting this research under the supervision of Dr. Paul Quinn and Dr. Justin Smoyer.
The aim of the research is to determine the characteristics regarding the Short Circuit Current (ISC) and the Open Circuit Voltage (VOC) of these solar cells while they undergo extreme conditions.
The solar cells being handled are very similar to what you would see in your everyday solar panel. These cells, however, are special because they are intended for use in outer space. To mimic the conditions of space, a cryostat, which is displayed in the image above, is being utilized.
Within the cryostat lies the solar cell itself, while two industrial-grade vacuum pumps lower the amount of pressure within the apparatus. Also attached to the cryostat is a large container that holds liquid nitrogen (N2). This liquid nitrogen hovers around 77° Kelvin, or nearly -200° Celsius, and is pumped into the cryostat.
These two components acting together can, for the most part, recreate the conditions that a solar cell would typically experience in space. A consistent light source is then shone onto the cell while the Current and Voltage characteristics are collected.
Like any other research project involving precise equipment, there have been quite a few hiccups. During the initial stages of working, several factors such as reducing ambient light effects, getting steady temperature readings, and even the manufacturing of the cells became issues. Some cells had different base characteristics because of manufacturing tolerances, which poses a huge issue when trying to find consistent data.
After resolving the issue and beginning to collect solid data, an interesting result had begun to emerge. It seems that after giving the solar cell a cold shock at -200°C for hours at a time, the VOC rises, but the effect is only apparent at extremely low temperatures. At standard room temperature, the VOC boost it had received at -200°C drops to nearly zero.
This effect has not yet been confirmed with more than two solar cells at the moment, but the project is still underway. The researchers hope to gather far more data that supports this effect before publishing any findings. In May of 2019, they hope to attend a conference and present a poster with their results to earn feedback and start making strides towards their next goal with the project.