Israeli Breakthrough Boosts Super-thin Solar Cell Generation by 30%

Twist on light-trapping technique combines ray-based light trapping with wave-optics absorption.

solar panels on Knesset
Olivier Fitoussi

Man may have inched closer to weaning himself off fossil fuels with an improvement in solar cell technology announced in Israel. The innovation, improving how the cells trap light, boosts the efficiency of electricity generation of ultra-thin solar cells by more than 30% without using costly new materials, say the scientists.

Their invention means we should be able to generate more electricity for less money, using less material.

In general, the way to make solar cells more cost-effective has always been to make them thinner (using less material), without impairing their ability to produce power. In practice, that means reducing the thickness of the cells’ light-absorbing layers (which turn light into electricity) without compromising their efficacy.

Physicists have been trying to work with active layers thinner than the typical wavelength of sunlight itself. The problem is that such thin layers do not effectively trap the light because at such lengths, the light behaves like a wave.

Trapping the light inside the cell would lengthen the path of the beam through the active layer. That in turn would increase the absorptivity of the layer. (In chemistry and physics, “absorptivity” is a measure of how well a material or chemical absorbs light.)

The team’s invention is a new method that combines ray-based trapping with wave-optics absorption, explain Dr. Avi Niv of Ben-Gurion University of the Negev, Prof. Avner Rothschild of the Technion-Israel Institute of Technology and others in their paper “Separation of Light Confinement and Absorption Sites for Enhancing Solar Water Splitting” in the Journal of Materials Chemistry.

They achieved this by structurally separating the trapping and absorption sites within the cell. 

First the light is trapped in a thick substrate layer, which feeds the energy into a subwavelength-thick hematite layer. The result, says the team, was enhancements of more than 30% in the cell’s power production – and the team predicts they can reach 40% and counting.

The method was developed for iron-oxide cells designed to produce hydrogen by splitting water, but could achieve its goal for other types of cells as well.

“Finding a way to harness ray optics for boosting the absorption of ultrathin cells, as was done here, could have a great impact on the future of solar cells,” Niv stated.