Thin-Film Photovoltaics
It is a great challenge to capture the solar radiation in one micrometer or less of photoactive material and it is certainly worth every effort. Thin-film photovoltaics means: low material usage and flexible, lightweight solar modules at competitive costs. This will widen the application window of traditional photovoltaics. At ECN Solar Energy, 25 scientists and technicians are proudly working on present and future generations of thin-film photovoltaics in national and international partnerships.
Film-silicon photovoltaics
We are developing deposition processes for inline manufacturing of high-efficiency thin-film silicon solar cells. This work is based on the use of stainless steel foil as a cheap and light-weight substrate. On the substrate, barrier, reflector, silicon and transparent conductive oxidelayers are subsequently deposited in a semicontinuous fashion. A multi-chamber plasma-enhanced chemical vapor deposition system will become operational in 2006. The system includes microwave and other sources for high-rate deposition of intrinsic and doped silicon layers, at a foil width of 30-40 cm.
Impression of multi-chamber PECVD system for roll-to-roll production of thin-film silicon PV on flexible substrates (installed at ECN in 2006).
Dye sensitized solar cells and devices
Dye-sensitized solar cells are based on the use of nanocrystalline metal oxide layers (TiO2, ZnO...) and some form of conducting material (e.g., a liquid or gel electrolyte). A dye is adsorbed onto the porous metal oxide surface. The dye acts as sensitizer by injecting electrons into the metal oxide upon illumination. Advantages of this technology include a very simple manufacturing process, based on the use of cheap and widely available materials.
Specially designed laminator for dye sensitized solar cells.
At our laboratory, a world-record efficiency of 8.2 % has been obtained in 2001. We develop manufacturing processes for liquid- and solid-state versions of this new PV technology. A baseline for semi-automated fabrication of 10x10 cm2 devices has been constructed. Our R&D is also targeting long-term stability under high stress factors. Please see the baseline video on this website!
Certified 8.18% record efficiency for a 2.5 cm2 dye sensitized solar cell.
Polymer solar cells
Organic materials are candidates for future photovoltaics. Conducting polymers have promising characteristics, and the corresponding “plastic” solar cells have shown great progress in efficiency.
ECN develops with its partners processes for optimization of bulk heterojunction polymer solar cells with respect to efficiency and stability. We work on polymer/fullerene (“bucky balls”), polymer/polymer and polymer/metal oxide devices. Part of this work is carried out within the Dutch Polymer Institute, DPI.
Performance improvement of polymer:polymer solar cell over recent years.
Innovative concepts
Solar cells do not capture all radiation coming to earth: in particular, cells are not very sensitive in the ultraviolet and infrared region. So why not change ultraviolet and infrared radiation into photons that better match the spectral response region of solar cells? Luminescent flat plate concentration uses the principle of photon conversion as an important step towards full spectrum utilization and high efficiency technologies.
Luminescent flat plate concentration: solar irradation is absorbed by luminescent particles and re-emitted by internal reflection towards the solar cell.
