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n a 1931 conversation with Henry Ford, Thomas Edison said, “We are like tenant farmers chopping down the fence around our house for fuel when we should be using nature’s inexhaustible sources of energy – sun, wind and tide. I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait until oil and coal run out before we tackle that.”

And tackle that we did with photovoltaic cells made up of materials called semiconductors, typically silicon, that convert sunlight to energy.

A warming planet, however, reduces the efficiency of solar-energy technology. That’s because solar-panel efficiency drops by .5 percent every time the temperature rises by 1 degree Celsius.

Sun shining on a solar cell excites electrons to a higher energy level due to the charge it creates. But when the cell is hot from the start, electrons are already in this excited state, which in turn produces less electricity

So, what now?

Solar technology is becoming more efficient, however. Researchers are developing cutting-edge materials and manufacturing models; multi-layer photovoltaic cells that absorb light from different parts of the spectrum like ultraviolet, visible light and infrared; and advanced technology like perovskites, whose specific crystal structure is highly efficient at converting sunlight to electricity.

Chinedu Ekuma, a physics professor at Lehigh University, sees the problem, particularly in the warmest climates, and possible new solutions.

“With rising global temperatures, solar panels are at risk of losing efficiency as excessive heat decreases their ability to convert sunlight into electricity.

This can undermine solar energy’s effectiveness in regions experiencing prolonged heat waves, pushing researchers to innovate materials that perform well even under extreme environmental conditions,” Ekuma says.

Ekuma’s research, funded in part by the U.S. Department of Energy, has produced a quantum material creating unparalleled solar-cell efficiency rates expected to contribute to next-generation, high-efficiency solar cells.

“Our newly developed quantum material, which incorporates intermediate band states, allows for a higher level of photon absorption and carrier generation. This innovation facilitates the generation of more than one electron per photon, pushing quantum efficiency beyond traditional limits, up to 190 percent, providing an exciting leap forward for photovoltaic applications,” Ekuma tells KUST Review.

This is especially significant because it implies the potential to exceed the Shockley-Queisser limit, which represents the theoretical maximum efficiency of a single-junction solar cell under standard conditions at 100 percent. In order to do so, the efficiency would have to exceed a maximum solar conversion efficiency of around 33.7 percent.

This limit exists because not all sunlight has the right energy to be converted into electricity. Some bounces off without being absorbed. Some is lost as heat or is relaxed into lower energy states that aren’t used. Some can’t maintain the excited electron state and defaults to its original states before it can be used. And some photons simply don’t have enough energy to boost the electrons.

Obstacles and applications

Ekuma’s team doesn’t foresee major obstacles to implementing their material into current solar energy systems. But scaling up to a commercial level of production and implementing the new material into existing technologies is going to take research and reduced cost, Ekuma says.

Ekuma’s material could pose solutions for countries where the temperatures are among the highest.
These places include the Middle East, where more energy is used for cooling than anywhere else on the planet.

The region has over 300 days of sunshine each year. According to Rystad Energy, it is expected to reach solar capacity of close to 23 gigawatts of power by the end of 2024.

Solar energy is expected to reach close to 50 percent of the regional power supply by 2050.

The Middle East and North Africa Region signed a pledge at the 2023 COP28 event hosted in Dubai to add 62 gigawatts of renewable energy over the following five years. Of that, 85 percent will be solar.

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