Printed PV Making Progress
Production announcements, investor activity and scientific progress are continuing to make exciting news in printed PV technologies. Printed electronics describes a broad set of technologies that use lower cost printing technologies (i.e. offset lithography, screen printing, gravure), rather than deposition and etch, that are useful for a multitude of applications not typically associated with silicon-based electronics, such as flexible displays, smart labels, animated posters, and photovoltaics. They include very small sizes, such as cell phone components, or very large (literally thousands of square meters) applications such as outdoor signs, displays and PV.
Unlike silicon microelectronics, printed electronics can be bent, shaped and integrated into irregular surfaces, such as architectural products. Flexible solar panels could feature lower product costs, lower shipping costs and lower install costs than traditional silicon wafer PV encased in glass.
According to a new report from NanoMarkets, the market for electronic inks and related substrate materials used in manufacturing printed electronics is expected to grow from over $1.1 billion ($US) in 2008 to over $11 billion by 2015. The global market for all printed electronic applications today is estimated at just under $1.2B. NanoMarkets estimates this market will increase to a $10B market by 2012, and a $300B market is projected by 2025. The largest segment of this market is projected to be batteries and PV. Nanomarkets estimates that printed photovoltaics are expected to consume more than $400 million in semiconductor materials by 2015.
According to the report, by then the photovoltaic industry will have overcome challenges to printing CIGS materials (copper indium gallium selenide ) and organic photovoltaics will have found significant addressable markets in building integrated photovoltaics.
Printing innovations make high volume production of PV materials at low cost, using green materials and on flexible substrates possible. Most of the printing methods used today, including offset, gravure, flexo and ink jet can be adapted to flexible PV materials. Proponents claim that printing is simpler, more effective and more robust than vacuum deposition techniques such as sputtering or evaporation which have conventionally been used to fabricate thin-film solar cells.
Global Solar (www.globalsolar.com) uses CIGS inks printed on a stainless steel flexible substrate, claiming 10% efficiency. Global Solar recently expanded production from a 33,000 sq. ft. factory to a new 100,000 sq. ft. facility in Tucson, Arizona and a 32,000 sq. ft. factory in Berlin, Germany, increasing the company’s capacity from 4.2 MW to 75 MW. Global Solar plans to put an additional 100 MW into production at the end of 2009, and 175 MW in 2010.
NanoSolar (www.nanosolar.com) has announced the building of a large scale plant to begin producing photovoltaic cells using a printing type process. In April, EDF Energies Nouvelles, who have been described as the world’s largest electric utility, announced the signing of a photovoltaic panel supply master agreement with Nanosolar and a $50 million investment in the company. Nanosolar utilizes a nanostrucutred CIGS ink on a metal foil substrate that the company claims is more than 20 times higher than that of the stainless steel used by others. Roll-to-roll processing on rolled foil substrates that are meters wide and miles long can be processed with very high throughput (and thus minimal capital cost) in equipment with a very small footprint (view video).
Konarka Technologies, Inc. (www.konarka.com) has developed polymer photovoltaic technology in a variety of form factors for commercial, industrial, government and consumer applications. Today, they are investigating dye-sensitized titania solar cells, organic photovoltaics, tandem cells, and materials that generate multiple electron-hole pairs. In March, the company claimed to have achieved the first-ever demonstration of manufacturing solar cells by highly efficient inkjet printing.
G24 Innovations Limited ("G24i") located in Cardiff, Wales (www.g24i.com) claims to be the first facility ever to produce solar cells with hybrid dye-sensitized thin-film (DSC) and organic PV (OPV) cells using automated "roll-to-roll" manufacturing processes. DSC technology has been described as ‘artificial photosynthesis’ that uses an electrolyte, a layer of titania and ruthenium dye. Australia-based Dyesol (www.dyesol.com) is another firm specializing in DSC, but currently offer solar products only in glass panels and tiles. Plextronics, Inc. has announced the introduction of its ink systems for organic solar cell fabrication in research applications. They offer a ready-to-use ink system that consists of two inks custom-designed to work together: a p/n photoactive ink and a hole transport ink that are both solution-processable.
In Japan, Mitsubishi Chemical Corp. is starting a big "Project PV," focusing on small-molecule organics solution coated on flexible substrates (Solid State Technology, August, 2008. With coatings of small molecule organics, Mitsubishi plans to deliver better performance than the more solution-processed polymers. Their technology reportedly can can be simply coated on and then heat-treated, without need for more costly vacuum deposition. It uses tetrabenzoporphyrin for the p-type semiconductor and a transparent conductive fullerene for the n-type, with efficiency currently of about 3.4%. The company plans to sample a 7%-efficient product by 2010.
While questions remain about the efficiency, competitiveness, durability and longevity of printed PV technologies, they appear certain to play an increasingly important role in the diverse PV marketplace.