Chemical engineers at the Massechusetts Institute of Technology have found a way to concentrate solar energy 100 times more than a regular photovoltaic cell.
Carbon nanotubes were used to form antennas that capture and focus light energy, potentially allowing much smaller and more powerful solar arrays.
Solar cells are usually grouped in large arrays, often on rooftops, because each cell can generate only a limited amount of power. “Instead of having your whole roof be a photovoltaic cell, you could have little spots that were tiny photovoltaic cells, with antennas that would drive photons into them,” says Michael Strano, Associate Professor of Chemical Engineering and leader of the research team.
The antenna consists of a fibrous rope about 10 micrometers long and four micrometers thick, containing about 30 million carbon nanotubes. The research team built a fibre made of two layers of nanotubes with different electrical properties. When a photon strikes the surface, it excites an electron to a higher energy level, which is specific to the material. The interaction between the energized electron and the hole it leaves behind is called an exciton. Because of the specific properties of the materials, the excitons in the outer layer flow to the inner layer, where they can exist in a lower energy state. The interface between the semiconductor and the nanotubes separates the electron from the hole, resulting in an electrical current.
Their new antennas might also be useful for any other application that requires light to be concentrated, such as night-vision goggles or telescopes.