Cheap and flexible tiny plastic devices hold the key to three times better efficiency of organic solar cells, according to scientists at Princeton.
The team led by Stephen Chou, an electrical engineer used metal and plastic sandwich-like nanostructure that collects light. The increase in efficiency was estimated to be 175%. Chou is certain that this technology will be equally successful when used in conventional inorganic solar collectors, although this part of the work is still ongoing.
The nanostructures capture all light that enters the sell, while at the same time they prevent it from escaping the cell. This is possible thanks to the so called subwavelength plasmonic cavity, or a “sandwich”. The results were striking- a solar cell which reflects 4 % and absorbs 96% of the light that enters. In addition, the efficiency was 52% higher than this of a conventional solar cell.
And this is not all- the above numbers are in the case of direct sunlight. If the solar cell is hit by sunlight at large angles, as it is on a cloudy day, the efficiency reaches 175% higher values.
The device has two layers. The top one, also referred to as the window layer, contains a thin metal mesh with diameter of the holes equaling 175 nanometers. This mesh is used instead of the conventional indium-tin-oxide (ITO).
The bottom layer of the sandwich is the same as the ones used in commercial solar cells, while between the two layers, the structure contains a thin strip of semiconducting material.
The device works that well mainly because the all features of the cell are smaller than the wavelength of the incoming light. The team established that these three subwavelength structures trap the light and hold it there. These new solar cells are called “plasmonic cavity with subwavelength hole array” or PlaCSH, as the scientists call them.
According to the team, the manufacturing process will be extremely cost-effective. The system was not only developed, but also optimized so that it can be used in various fields and industries depending only on the solar collector.
The findings can be found in the journal Optical Express, with a lead author Wei Ding, Chou’s graduate student.