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NanoPower Research Labs

Organic/Polymer Photovoltaics

The recent demand for alternative energy production has propelled considerable interest in next-generation photovoltaics technology. Of the many types of solar cells being developed, the bulk heterojunction polymer devices can be considered one of the most disruptive technologies. This is due to the lure of a low cost liquid solution that can easily be deposited onto either rigid or flexible substrates. The most successful device architecture to date has an active layer containing a composite blend using derivatized fullerenes (e.g. PCBM[60]) and conducting polymers from the polyphenylenevinylene or polythiophene class of structures. Significant progress has been made to optimize the appropriate composite morphology to maximize absorption and carrier transport through solution processing, annealing, and material selection. This work has led to small active area devices (generally <<1 cm2) having confirmed power conversion efficiencies of 4.8% under AM1.5 illumination.

(a) Schematic of a typical device architecture and (b) energy level cascade depicting donor:acceptor absorption and carrier transport.

Significant progress has been made to optimize the appropriate composite morphology to maximize absorption and carrier transport through solution processing, annealing, and material selection. This has led to state-of-the-art developments to date on small active area devices (generally <<1 cm2) having confirmed photovoltaic conversion efficiencies as high as of 4.8% under 1 Sun Air-Mass 1.5 or AM1.5 illumination. Unfortunately, the host polymers have bandgaps that are not well suited solar spectrum (i.e., ~2 eV), their carrier mobilities are low, and the resulting solar cells are not very environmentally stable. The prospect of polymer solar cells emerging as a more sustainable technology than silicon relies upon the development of higher efficiency and robust environmentally stable devices. This project is directed towards fundamentally investigating both of these issues with the objective of the development of high efficiency (> 20%) low-cost organic solar cells (< 10 cents/kWhr) and therefore long-lived (> 1 year with less than 1% efficiency degradation).

Recent Publications:
Ryne P. Raffaelle, Annick Anctil, Roberta DiLeo, Andrew Merrill, Oxana Petritchenko, and Brian J. Landi, “Dye-Sensitized Bulk Heterojunction Polymer Solar Cells”, Proc. of 33rd IEEE Photovoltaic Specialists Conf. 1, pp. pending (2008).
Landi, B. J.; Raffaelle, R. P.; Castro, S. L.; Bailey, S. G. “Single Wall Carbon Nanotube-Polymer Solar Cells.” Prog. Photovolt: Res. Appl. 2005, 13, 1-8.
Landi, B. J.; Castro, S. L.; Ruf, H.J.; Evans, C.M.; Bailey, S. G.; Raffaelle, R. P. “CdSe Quantum Dot-Single Wall Carbon Nanotube Complexes for Polymeric Solar Cells.” Sol. Energy Mater. Sol. Cells. 2005, 87, 733.
Landi, B.J.; Evans, C.M.; Worman, J.J.; Castro, S.L.; Bailey, S.G.; Raffaelle, R.P. “Noncovalent Attachment of CdSe Quantum Dots to Single Wall Carbon Nanotubes.” Mater Lett. 2006, 60, 3502-3506.