The presentations with a focus on thin film photovoltaics covered topics relevant to both organic and inorganic technologies but also discussed the importance of incumbent technologies.
Maikel van Hest, representing the National Renewable Energy Laboratory (NREL) in the USA for instance, described innovations in transparent conductors but didn't fail to point out the importance and width of use of ITO technology.
At the same time Maikel described topics relating to atmospheric processing of photovoltaic technologies, both organic and inorganic ones, utilizing deposition techniques ranging from CBD for CdTe technologies to inkjet printing of Ag fingers on silicon cells to spray or print deposition of active layers in organic photovoltaics.
Giorgio Cellere on the other hand, representing Applied Materials Baccini, described advances on conventional screen printing technology as utilized on silicon wafer solar cells. Efforts to increase efficiency have led to significant developments both in printing of silver, as well as work on selective emitters. "In 2015, 100 million ounces of silver will be used in photovoltaics, out of a total of 243 million ounces produced" Giorgio stated during his presentation and continued to describe the development of the accuracy of screen printing as applied to the solar cell sector. In 2006, screen printers were depositing 150micron wide lines, with a 15 micron thickness by single line printing. Fast forward to 2012 and 50micron wide lines can be deposited with a 25 micron height, with double pass printing.
Applied Materials Baccini Screen Printer
Christian Pho Duc, VP of Sales EMEA & India for Nanosolar discussed the company's printed approach in the manufacturing of flexible CIGS on aluminium foil. Using nanoparticle printing and non-vacuum annealing in a Metal Wrap-Through (MWT) structure leads enables thin contact layers.
The company is currently reliably producing panels with 11.5% efficiency, eyeing improvements in efficiency that will lead to panels of 14% efficiency by 2013. In terms of cost projections, as seen in the graph below, the company claims a much faster reduction in cost with volume when compared with technologies such as c-Si and CdTe which have a more cost-intensive manufacturing structure.
Nanosolar projections: cost per watt vs. production volume
Alexander Meeder from Soltecture discussed a different approach to manufacturing and commercializing CIGS, describing the company's higher efficiency cells that will be targeting the building integrated PV sector. The company's roadmaps are also aiming at efficiencies over 16% in the near future, with a multitude of improvements being investigated, including the substitution of the CdS buffer layer, reduction of defect density in the absorber and an improved module design in order to minimize scale-up losses.
Soltecture's power distribution and increase in module power/efficiency over time
Novaled - Heliatek
Contributions from Novaled and Heliatek gave an update of the landscape for organic photovoltaics, the "underdog" that is determined to catch up with the leading solar technologies and claim a significant market share in the near future.
Heliatek flexible solar cell
Heliatek's approach is based on p-i-n tandem cells; the company, through precise optical engineering works on placing the absorber layers in the respective interference maxima. Back in 2009, Heliatek was demonstrating cell efficiencies of about 6% but through a lot of work in optimizing materials, including the development of wideband strong absorbers such as the one showcased below, the company demonstrated at the end of 2011 a solar cell with a certified 9.8% efficiency and is currently in the process of certifying cells which are expected to achieve over 10% efficiency.
Heliatek broadband absorber with strong absorption characteristics
The company is also progressing in transferring its technology from glass to PET foil as well as working on substituting ITO with other transparent conductors such as Cambrios' silver nanowires, having achieved 8.5% efficiency with those cells.
Finally Novaled, a company better known for the development of materials for OLED display and lighting technologies discussed its work on advanced charge transport materials for small molecule organic solar cells. The Heliatek record 9.8% efficiency cell described above included proprietary absorbers developed and synthesized by Heliatek but also Novaled dopants.
Dr Steffen Pfuentzer presented Novaled's strategy and pointed out that the company aims to develop and provide key enabling organic materials to key players in organic photovoltaic technologies, whether based on polymer, small molecule or dye sensitized solar cells.
For more attend Printed Electronics USA, December 5-6, 2012