Two-layer solar cell to achieve 42 percent efficiency

July 4, 2011 | Source: Technology Review
Quantum Dots

Each of these 16 dots is a solar cell made up of quantum dots (credit: Ted Sargent)

In a paper published inĀ Nature Photonics, University of Toronto researchers report the first efficient two-layer solar cell based on colloidal quantum dots (CQD) to capture both visible and near-infrared rays.

CQDs are nanoscale materials that can be tuned to respond to specific wavelengths of the visible and invisible spectrum. By capturing such a broad range of light waves — wider than normal solar cells — tandem CQD solar cells can in principle reach up to 42 per cent efficiencies.

The best single-junction solar cells are constrained to a maximum of 31 per cent efficiency. (In reality, solar cells that are on the roofs of houses and in consumer products have 14 to 18 per cent efficiency.)

The researchers expect that in five years, solar cells using the graded recombination layer paper will be integrated into building materials and mobile devices.