Konarka is a company that develops solar panel using nano-enabled polymer photovoltaic materials. This polymer material, or as Konarka called PowerPlastic, is a semi-conductor organic material that are thin, lightweight, and very flexible. Comparing to traditional solar panel, PowerPlastic provides better performance, lower cost, and lower toxicity. Not only that, PowerPlastic can absorb low light level efficiently. The main component of Konarka’s photovoltaic cells is nanoscale titanium dioxide particles coating, a light-sensitive dye that generates electricity when light shines on.

PowerPlastic solar panel is created using roll to roll manufacturing process. Roll to roll process is the process in which transparent electrode, printed active material, primary electrode and substrate are printed onto transparent packaging to make a solar panel. This manufacturing process is inexpensive, environmental friendly, and simple. Currently, Konarka is invested by US military, the National Science Foundation, DARPA, and the Department of Energy, the Department of Commerece, etc. Konarka’s solar panel is a great prospect of future alternative energy source.

(Macroelectronics.org will start a series on thin film flexible solar cells. Stay tuned!)

Solar cells are devices that convert solar energy to electrical energy. The process in which the solar cell converts solar energy to electricity is called photovoltaic. Traditional solar cell is mostly made out of silicon, a well-known semi-conductor. When the sunlight hits the solar cell, photons from the sunlight is absorbed by the semi-conductor. The photons then hit the atoms causing electrons to be kicked out of atoms. The movement of electrons produces electricity (see figure).

Silicon is a brittle material and fractures at very small deformation. This poses a significant challenge to make and handle large area solar cell panels. To further reduce the cost to harvest solar energy, there have been emerging efforts on developing thin film solar cells that can be fabricated on thin plastic foils by a roll-to-roll process. The functional device material used in such thin film solar cells include organics/polymer film, gallium arsenide, copper-indium selenide, etc. However, so far thin-film solar cells are not as efficient as conventional solar cells. In the subsequent posts of this series, we'll review the currently available technologies of thin film solar cells.

The use of silicon based solar panels are predominant in today's market. The silicon-based solar panels are often heavy (because of the glass used as substrates), which in turn lead to high shipping and installation costs. A better alternative, thin film organic-based solar panel, has gained great interest in recent years.

The researchers at Princeton, in 2004, demonstrated organic photovoltaic cells of improved efficiency by stacking two hybrid, planar, heterojunction organic cells in series. By using copper phthalocyanine as donor and C-60 as acceptor, they were able to collect both long and short wavelength solar energy and a maximum power conversion efficiency of 5.7% with an open voltage cirguit of 1.2 volts.

More recently, in 2007, researchers at the Gwangju Institute of Science and Technology (GIST) in Korea and at the University of California, Santa Barbara have announced the creation of a tandem solar cell. It better utilizes sunlight and has an efficiency of 6.5%. Through a three layer panel: one cell on top, a layer of nano titanium oxide in the middle, and another cell on the bottom, this design allows the top layer to absorb luminous light and the lower layer to absorb infrared waves. Furthermore, the lifetime of these organic-based photovoltaic solar cells can be lengthened through a special encapsulation process.

Conventional silicon-based solar cells cost $2.3 to generate one watt of electricity; the organic-based solar cells cost $0.1 to generate the same amount of electricity. It is expected that these organic-based solar cells will dominate the solar energy market through uses on windows, roofs, mobile devices, or even clothes etc. The total market for organic solar cells will be $1 billion in 2012 and $6 billion in 2014, as predicted by IDTechEx.

Here's the link to the Princeton research paper.

Here's a link to the GIST/UCSB research paper.

(via IDTechEx)