Ultrathin solar panels could potentially transform the renewable energy landscape. Much thinner than today’s standard panels, they require far fewer raw materials to manufacture. This significantly reduces production costs and makes them easier for manufacturers to integrate onto a wide range of surfaces.
However, one major drawback has held them back so far: lower efficiency. Thinner photovoltaic cells absorb less light, and part of the energy is lost through the back of the panel. To address this issue, researchers from the Iberian International Nanotechnology Laboratory came up with an unexpected solution: using gold to create a reflective layer beneath the photovoltaic cell. In a study published in the journal Solar RRL, they report an efficiency increase of 1.5 percentage points in ultrathin ACIGS solar cells ((Ag,Cu)(In,Ga)Se₂).
To achieve this result, the team developed what they call a “nanostructured mirror.” It consists of a 25 nanometer thick layer of gold covered with a nanoscale T shaped pattern, then encapsulated with aluminum oxide. This configuration reflects light back through the photovoltaic cell, reducing energy losses at the rear of the panel. “It works by ensuring passivation of the interface,” explains researcher Pedro Salomé.
The structure was created using a single step nanoimprint lithography process. Compared with traditional fabrication methods for nanostructures, this technique is cheaper, simpler, and faster. As a result, it opens the door to large scale manufacturing of these ultrathin solar panels.
This breakthrough could make it possible to produce flexible or curved solar panels that are easier to deploy on vehicles, buildings, or mobile devices. By combining reduced material use with improved performance, the researchers believe their approach could help ultrathin panels close the gap with conventional technologies.
While adding gold might seem like a luxury, the extremely small quantities involved mean the overall cost remains low. In return, the efficiency gains could significantly improve the economic viability of next generation solar technologies and accelerate their adoption across multiple industries.

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