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A recent advance in solar cell technology may pave the way for more efficient and lightweight energy solutions. Researchers from the International Iberian Nanotechnology Laboratory (INL), in collaboration with Uppsala University, have developed a new method to enhance ultrathin solar cells using a novel nanostructured mirror.
Ultrathin solar cells are appealing for their reduced material use, flexibility, and potentially lower production costs. However, making cells thinner can reduce their ability to absorb light, as some of the energy escapes through the back of the cell. To address this, the research team introduced a reflective structure designed to trap and redirect light within the cell.
The solution involves a thin patterned gold layer, coated with aluminum oxide, that acts as both a rear mirror and a passivation layer. This nanostructure reflects light that would otherwise be lost, giving it a second chance to be absorbed and converted into electricity. At the same time, the aluminum oxide layer reduces surface defects that typically cause energy loss through electron recombination.
Rather than relying on complex fabrication methods, the team applied a single-step nanoimprint lithography process to create the patterned mirror. This technique allows for faster, more scalable production—key for commercial applications.
The improved design was tested on ACIGS (Ag,Cu)(In,Ga)Se₂ thin-film solar cells, which already have a strong track record for efficiency. With the mirror integrated, the cells showed an efficiency gain of approximately 1.5%, primarily due to better light absorption. The team also determined that the optimal manufacturing temperature is around 450°C, which prevents degradation from gold diffusion and enables use on flexible substrates.
This innovation addresses two major technical hurdles—light management and interface passivation—in a cost-effective and scalable way. Potential applications include solar panels for buildings, vehicles, or mobile electronics where weight and flexibility are critical.
The full research findings are published in the journal Solar RRL.
