Physical Society Colloquium

Nonlinear optical nano-photovoltaics

Jean-Michel Nunzi

Department of Physics, Engineering Physics and Astronomy /
Department of Chemistry
Queen's University

A photovoltaic (PV) technology that is not limited to the Shockley�Queisser efficiency limit and that is amenable to low-cost and large-area production requirements is studied in our team. It does not rely on the photoelectric effect, which is at the origin of the efficiency limits of the PV effect in semiconductor devices, it uses optical rectification of sunlight as a concept for high efficiency PV cells.[1] Antennas efficiently convert waves into a potential difference, which must be rectified to DC or low frequency current to be useable for energy production. This particular type of antenna was named rectenna. EM-wave to DC conversion can in principle be done at solar frequencies with much higher conversion efficiency (85%),[2] than present day photovoltaic technologies. The idea of collecting solar EM-radiation with rectennas was proposed forty years ago,[3] but suffers that rectification should be achieved at optical frequencies where diodes don't exist. We proposed a practical design in which light rectification is achieved by metallic nanoantenas covalently coupled to molecular diodes.[4] We started this project investigatin nonlinear absorption in a poly (3-hexylthiophene) (P3HT) PCBM fullerene blend, one of the most popular organic solar cell's materials. The output photocurrent of the photodiode was interpreted in terms of the three-photon absorption properties of the P3HT:PCBM blend at 1550 nm.[5]

Could the concept be extrapolated to high efficiency solar cells? We review some essential phenomena happening in nanostructured organic solar cells and how they may limit their efficiency. We then show how the optical antenna technology revisited with plasmonics [6] and organic rectifiers [7] should permit the development of an ultra-high efficiency PV technology that is compatible with large-area fabrication (self assembling) and low-cost (plastic) technologies. We discuss its relation-ship with second and higher-order nonlinear optics.

[1] Goswami D.Y., Vijayaraghavan S., Lu S., Tamm G., Solar Energy 76 (2004) 33
[2] Corkish R., Green M.A., Puzzer T., Solar Energy 73 (2002) 395
[3] Bailey R.L., J. Eng. Power 94 (1972) 73
[4] Nunzi J.M., Proc SPIE 7712 (2010) 771204
[5] Mirzaee S.M.A., Rao B.S., Nunzi J.M., Proc. SPIE 8915 (2013) 891514
[6] Liu F., Nunzi J.M., Org. Electr. 13 (2012) 1623
[7] Sentein C., Fiorini C., Lorin A., Nunzi J.M., Adv. Mater. 9 (1997) 809