28 May 2009
New Energy Technologies (Washington, DC) has developed ultrasmall transparent solar cells that can be coated onto glass, plastic or even paper.
A tinted transparent coating that can generate electricity from both natural and artificial light exploits ultrasmall solar cells made from flexible polymer materials.
New Energy's SolarWindow technology uses an organic solar array made from conducting polymers that are claimed to convert light to electricity more efficiently than silicon, which is commonly used in solar-cell manufacture.
"Our use of these new, readily available and easy-to-apply ultrasmall solar cells directly addresses numerous commercial and technical limitations posed by conventional PV materials," said Meetesh Patel, CEO of New Energy Technologies. "I'm particularly impressed by the potential application of this technology in areas where direct exposure to sunlight is limited or unavailable, since these cells have demonstrated a special ability to generate electricity in both natural and artificial light conditions."
A recent study in the Journal of Renewable and Sustainable Energy by researchers at the University of South Florida found that an organic solar array based on a 1 mm2 single cell produced an open-circuit voltage of 7.8 V and a short-circuit current of 55 µA under simulated air-mass 1.5 illumination with an intensity of 132 mW/cm2. They concluded that the technique could result in practical microarrays as small as 0.01 mm2.
Unlike other solar technologies, New Energy's solar cells generate electricity not only from the visible radiation found in sunlight but also by using the visible light found in artificial illumination, such as the fluorescent lighting typically installed in offices and commercial buildings. While the majority of today's solar cells can only be installed where direct sunlight is available, New Energy's cells could be installed close to any source of visible light.
The solar cells could also allow fabrication of solar arrays on a broad range of substrate materials, such as glass, plastic, and even paper. Made of natural polymers that can be dissolved into liquid for easy application, the cells do not require expensive and complicated high-temperature or high-vacuum production techniques common to other solar coatings.
The superior optical absorption properties provided by the new cells mean that the films need only be 0.1 µm thick, according to the company. Conventional thin films are typically several microns thick, which inhibits their use for applications that require transparency – for example, solar windows for application in homes, offices and commercial buildings.