Replacing the front layer of indium tin oxide, zinc oxide or cadmium sulfide in a PV cell with a carbon nanotube conductive layer would result in a cell with greater efficiency because the conductivity of the nanotube material would be greater and the reduced thickness would provide greater light transmittal than present materials. Carbon nanotubes in the order of 10 nm could be fabricated in either the highly conductive metallic form or the semiconductor form. The story did not say if the concept had been reduced to practice.
NASA Tech Briefs, June 2005, pp. 32, 34
If this story were not from such a highly respected publication, this review would not be considered. What has been reported is a phenomenon which violates the fundamentals of classical optics which says that light cannot pass through a hole smaller than its wavelength. The opposite has been reported by the Louis Pasteur University in Strasbourg and the Tokyo Institute of Technology. Metal films perforated with the nano holes not only display light transmission, but they also show that twice as much light gets through as would be expected from materials with larger holes. By scribing the materials with concentric grooves, the light can be increased by a factor of 20.
The explanation involves defining ‘plasmons’ which are tiny electron waves set up on the material when struck by light. The plasmons create tiny magnetic dipoles around the hole which line up with the polarization of the incoming light.
The phenomenon is described as ‘extraordinary transmission’ and is anticipated to improve lasers and data storage applications. (Ed. note: Why not apply it to PV to improve transmission through the front conductive layer?)
IEEE Spectrum, July 2004, p. 18
(July 2003) Ener1 tests new prototype solar cell. The new high-efficiency solar cell is based on photo-electro converters (PEC) to permit high utilization of available solar energy for electrical energy generation and storage. In developing its new PEC-based solar cell, Ener1 used several techniques including its new vacuum spraying technique and high-efficiency photo-lithographic process. Ener1’s tests of its new PEC-based solar cell indicate significant improvements in key solar cell characteristics such as efficiency (19-21%) and increased power.
The Company’s tests indicate that its PEC-based solar cell system is stable under radiation and is suitable for space-based applications.
United Solar Systems and Bekaert ECD Solar Systems inaugurates world’s largest thin-film solar cell manufacturing machine and related assembly equipment. The installation is at its Bekaert ECD Solar System facility in Auburn Hills, Michigan. The new machine is capable of producing nine miles of solar cells in three days’ time making it one of the four largest producers of solar cells and related products in the United States.(08-02BD77-10)
Heriot-Watt University’s School of Textiles in Scotland researches the production of fabrics with solar cells. Professor John Wilson is working on creating solar cells which are as much as 100 times thinner than those cells used today in solar panels made of crystals of silicon. Prof. Wilson believes that a workable cell can be created by depositing thin films of silicon on to a glass substrate. Theoretically, these films, only a few microns thick, could be laid in to fabrics or clothing fibers prior to the weaving process. It is hoped that the textiles could be efficient enough to produce 100 Watts per sq. meter in very sunny locations. Improvements in cell efficiency might be offered by the latest crystalline silicon nanotubes. Perhaps such a patch on a jacket or bag could power a laptop or trickle-charge a mobile phone or PDA. (07-02BD76-3)