An NYU Tandon-led research team has developed a novel technique to significantly enhance the performance of cadmium telluride (CdTe) solar cells. Unlike conventional silicon panels that use thick layers of silicon, these solar cells use a simpler, less expensive approach—depositing an ultra-thin layer of cadmium and tellurium compounds onto glass.

This thinner design reduces manufacturing costs while helping the cells maintain their efficiency at high temperatures and in low-light conditions. Though less common than traditional silicon panels—the familiar dark blue or black panels seen on rooftops—CdTe solar cells are an emerging technology primarily used in utility-scale solar farms, currently accounting for about 40% of U.S. large-scale solar installations.

A persistent challenge with these cells, however, has been damage that occurs during a critical manufacturing step—when the metal wiring is added to collect electricity from the cell. The high-temperature process of applying these metal contacts can damage the material, particularly at the boundaries where microscopic crystal regions meet, like weak points between tiles in a mosaic. This damage creates barriers that reduce the cell’s power output.

In research published in ACS Applied Materials & Interfaces, the team found that applying an ultra-thin oxide coating—either aluminum gallium oxide (AlGaO_x) or silicon oxide (SiO_x)—before adding metal contacts like gold prevents this damage. The coating naturally collects at these vulnerable boundaries between crystal regions, protecting them while leaving the rest of the surface clear for electrical contact.

This simple and scalable solution has led to major improvements in the cells’ electrical output, increasing the maximum voltage they can produce by 13% and boosting their overall power generation.

“Silicon solar cells are rated at room temperature, but their performance drops as temperatures rise. You don’t have that problem with CdTe cells, which makes them particularly valuable in warmer regions like the Caribbean or near the equator,” said André Taylor, an NYU Tandon professor of chemical and biomolecular engineering and one of the paper’s authors.

The paper’s corresponding author is B. Edward Sartor, who was a doctoral student in Taylor’s lab when the study was conducted.

With the protective layer in place, the open-circuit voltage of the solar cells increased from 750 to 850 millivolts. The fill factor, another key efficiency metric, also improved, provided the oxide layer remained thin enough to avoid increasing electrical resistance.

“The AlGaO_x layer protects the cell when you’re evaporating the gold contacts, which come in at high temperature and condense on the surface. Without this protection, you damage the interface and create defects that lower device performance,” Taylor explained.

The oxide layer is applied through a simple spin-coating process, a widely used technique in semiconductor manufacturing that allows precise control over coverage. The researchers also found that the method works with different metal contacts, including gold and molybdenum, and that it shows potential benefits when combined with zinc telluride nitrogen-doped (ZnTe:N) buffer layers, which help facilitate the movement of positive charge carriers (holes) in the solar cell.

“This discovery suggests a promising path to making CdTe solar cells more efficient and reliable,” said Taylor. “It’s a straightforward adjustment to existing manufacturing processes that could potentially advance solar energy production.”

The research comes at a critical time for U.S. solar manufacturing. After losing the silicon solar cell market to China, CdTe technology offers a strategic opportunity to rebuild domestic manufacturing capabilities, with companies like First Solar leading the way. The technology also offers a unique sustainability angle: tellurium, a key ingredient, can be extracted from copper mining operations, where it was previously considered a waste material, potentially creating new economic value.