To date, under controlled laboratory conditions, the best cells can convert nearly half the sunlight they absorb into 44% electricity. Commercial cells convert less than half of this amount.
However, there may be hope. Scientists at Aalto University in Finland have revealed their design for a new light-trapping structure. They propose that a cell be covered with a regular array of silver nanoantennas that convert ordinary incoming waves into more exotic ones that propagate through the photovoltaic slab to increase efficiency.
Despite the fact this approach is still theoretical, it looks promising. The team demonstrated that the nanoantenna array can increase the overall spectral efficiency of solar cells that are not thick. The team calculates that anti-reflection coating loses approximately 7% of the light due to reflection and transmission accounts for 46% of the loss.
In sharp contrast to the conventional method still used, the Aalto scientists’ method loses only 20% to reflection and only 8% during transmission, meaning 6% more is absorbed due to the extra surface.
While more efficient overall, the fabrication costs have yet to be determined. Scientists do think the printing a nanoantenna array on a thin film can be cost-efficient, but they are unsure as to the overall cost on a large scale.