Photovoltaic cells made from the right combination of materials could break through the limited potential of solar power.

With today's common commercial and industrial solar cells converting sunlight into energy at a rate of 30-40% maximum, a 60% efficiency power conversion potential is groundbreaking. After 15 years of trial and error, a team of researchers at the Universidad Complutense de Madrid in Spain has fabricated an intermediate band (IB) solar cell using gallium phosphide and titanium that has the potential to deliver an energy conversion efficiency of 60%.

The upper limit on how much energy a solar cell can convert into electricity is related to the materials it contains, where under the best-case scenario, even the highest-quality silicon-based solar cells will still not be able to harness 77.3% of the sunlight absorbed, shedding the rest as heat.

To meet global renewable energy demands, countries would need to bulk manufacture and cover expansive acreage with solar cells – however, the more efficient the electricity generation, the smaller the footprint.

Enter Javier Olea Ariza and his team of university researchers, who have established a promising combination of gallium phosphide and titanium to make a more efficient solar cell. With energy output dependent on the electrical conductivity, or bandgap, of the semiconductor material,

Ariza and his team chose gallium phosphide, a semiconductor with a high bandgap, which is essential to increasing a solar cell's energy output.

The team built a one-square-centimeter-sized solar cell with a gallium phosphide-titanium absorber no thicker than 50 nanometers and metal contacts using gold and germanium.

Through a series of experiments testing transmittance and reflectance measurements, the team found that their prototype had a broader band due to enhanced light absorption at a wavelength above 550 nanometers.

The team first worked with these materials in 2009, taking the next 15 years to construct experimental devices with them. Even at this point, the prototype is still in the lab phase, and work remains to be done to resolve issues with solar cell construction by using different approaches to incorporating titanium in solar cells with the theoretical potential of around 60% sunlight conversion.

Ariza, however, is downplaying expectations due to the early stage of experimentation, telling pv magazine, "It doesn't make sense to think about it until we have a laboratory prototype in which we have solved the problems, and it has high efficiency."

While commercial deployment of this technology remains in the distant future, a solar cell delivering this enhanced performance is key to creating a sustainable future, not only by way of green energy, but also by the more economical and sustainable use of land and materials.