Polymer based Photovoltaics
R&D objectives
There is a growing interest in new generations of PV technologies and conversion concepts aiming at either very low cost or very high efficiency or a combination of both. It has been recognized that Organic/Polymer based PV can be considered as such a high-risk high-potential option since it has many attractive features like:
- Flexibility and light weight
- Semi-transparency
- Low-cost fabrication via high-throughput, low temperature printing techniques
- Easy integration in a wide variety of devices
- Tuneable properties of organic materials
- Can profit from experiences in the development/ commercialization of organic electronics like Light Emitting Displays (LEDs) and Field Effect Transistors (FETs)
Up to around 4 % efficiency on lab scale can be obtained for certain polymer-based solar cells. Despite the progress made in this field, it is clear that Polymer PV is still in its early infancy. Several research issues must still be addressed before polymer PV will become a practical technology. These include a further understanding of operation (interfaces, charge transport, morphology control) and stability of these cells. Novel materials are needed for a better spectrum utilization (band gap engineering, new device architectures). This should ultimately lead to higher power conversion efficiencies (>10 %), and lifetimes that are sufficiently long for practical use.
ECN's approach
ECN's research on Polymer PV forms part of a multidisciplinary research program in the Netherlands carried out in the frame of the Dutch Polymer Institute (DPI), which is a consortium of universities, research institutes and industry. Further funding is provided by the SenterNovem EOS program.
The specific tasks of ECN in the DPI program are:
- Device fabrication and optimization with the aim to improve efficiency and stability
- Technology development (printing and coating techniques, encapsulation)
- Accurate performance testing (IV, Spectral Response at standard reporting conditions, lifetime testing)
Published results
- For a recent overview of the Dutch research on Polymer based PV see:
http://www.ecn.nl/docs/library/report/2005/rx05016.pdf and references cited therein - A power conversion efficiency of 1.5 % at AM1.5 conditions was achieved for a polymer/polymer bulk-heterojunction solar cell, see: M.M. Koetse, S.C. Veenstra, submitted for publication
- A power conversion efficiency of ~ 1 % was achieved for a Polymer/ZnO bulk heterojunction solar cell prepared from a ZnO precursor; W. Beek, L.H. Slooff, Advanced Functional Materials, 2005, 15,1703-1707
Other interesting information
The general term Organic Based PV represents a broad class of concepts where organic materials form an essential part of the device. Examples are Dye-sensitized Solar Cells (nc-DSC), Molecular Organic Solar Cells made from relatively small organic molecules and Polymer Organic Solar Cells mainly based on electrically conductive polymers. For a good overview of the different concepts see:
MRS Bulletin, 2005, 30, pg 10-52
A report, based on the outcome of the Basic Energy Sciences Workshop on Solar Energy Utilization identifies the key scientific challenges and research directions (including Organic based PV) that will enable efficient and economic use of the solar resource to provide a significant fraction of global primary energy by the mid 21st century. The report reflects the collective output of the workshop attendees, which included 200 scientists representing academia, national laboratories, and industry in the United States and abroad, and the U.S. Department of Energy?s Office of Basic Energy Sciences and Office of Energy Efficiency and Renewable Energy.
http://www.sc.doe.gov/bes/reports/files/SEU_rpt.pdf
