Scientists demonstrate how integrating a radiative cooler with a multi-junction solar cell can enhance its power conversion efficiency.

Standing in the sun all day gets solar cells pretty heated. I know, it’s their job! But over time, heat degrades solar cells and lowers their power-conversion efficiency. New research was published this week may have found a way for radiative coolers to solve this problem at low cost without energy consumption.

Scientists from Pusan National University, Korea, successfully tested their theories on what kind of solar cells work best with radiative coolers, publishing novel insights for designing the next generation of highly efficient and long-lasting solar cells in Advanced Energy Materials on Dec. 22, 2021.

What is radiative cooling? Radiative cooling (RC) has emerged as a promising technique due to its simplicity and low cost. In RC, a micro-grating of glass, i.e. a two dimensional framework structure, is fixed onto the surface of the solar panel. The materials and placement of these gratings are such that light absorption is enhanced while heat (infrared radiation) is emitted through the atmosphere into outer space. This method has the additional advantage of not needing any external energy source to operate. Thus, RC can simultaneously reduce the temperature of the solar cell while increasing the energy input (light) for conversion into a voltage.

Research into RC as a technique applicable to solar cells remains nascent, and the influence of type of solar cell on RC efficiency remains to be seen. But researcher Gil Ju Lee thinks this could change things.

“In current solar cells, separate water or air cooling systems that require electricity to operate are needed,” explains Lee. “Using RC can mean transitioning to a completely eco-friendly and energy-free cooling system. Our research is the first theoretical and experimental demonstration of the effectiveness of radiative-cooler-integrated solar cells.”

A theoretical scouring of a wide range of solar cell-RC combinations showed that multi-junction solar cells (MJSCs) were most effective with an RC. To verify their outcome, they performed outdoor field tests on an RC-integrated InGaP/GaAs/Ge MJSC.

Under an approximately 900 Wm–2 direct sunlight, they achieved a 6°C temperature drop, 2% increase in open-circuit voltage, and 0.5 mA increase in short circuit current, thus demonstrating enhanced cooling performance and better power-consumption efficiency than conventional glass-mounted MJSCs without an RC.

“Before our study, research has largely focused on single-junction solar cells and computational evaluations,” Lee says. “Our study is the first to experimentally show that a more effective type of solar cell, the MJSC, benefits the most from RCs.” [Link]