Special Seminar Presented by the Stanford Optical Society
Light trapping for high-efficiency thin-film silicon solar cells
Dr. Corsin Battaglia
Institute of Microengineering, EPFL
Tuesday, May 03, 2:15 PM, Astrophysics 102/103
Refreshments at 2PM
Thin-film silicon solar cells have been identified as one of the most promising technologies to render photovoltaics, the conversion of sunlight to electricity, economically competitive with fossil-fuel technologies, as they are based on abundant, non-toxic materials and low-temperature processes. Advanced light trapping concepts are crucial to realize high-efficiency thin-film silicon solar cells, as the absorption coefficient of silicon is small in the near-infrared region. With properly engineered photonic nanostructures, sunlight can be trapped within the thin absorbing silicon layers, thereby enhancing light absorption and thus conversion efficiencies.
We present here the latest research developments in single-junction amorphous and tandem micromorph (amorphous/microcrystalline) silicon solar cells in our laboratory. Recently developed nanocrystalline silicon oxide layers [1, 2], deposited by plasma-enhanced chemical vapor deposition, enable the integration of photonic nanostructures until now considered too aggressive to maintain acceptable electrical cell performance. In combination with the optimized random pyramidal morphology of transparent conductive zinc oxide films, grown by chemical vapor deposition, outstanding light trapping capabilities are demonstrated [3] which have lead to several certified world record conversion efficiencies [4, 5]. To implement arbitrarily designed surface morphologies directly into functional cells, we recently fabricated transparent nanotextured front electrodes by ultraviolet nanoimprint lithography [6] and demonstrated cell efficiencies as high as for state-of-the-art zinc oxide electrodes [7]. We further present an innovative new method [8] allowing one to impose an arbitrary surface morphology onto transparent conductive zinc oxide films providing a versatile experimental platform in the quest to find the most efficient light harvesting scheme.
About the speaker
Corsin BATTAGLIA obtained his PhD in physics from the University of Neuchâtel, Switzerland in 2008 for his work on the structural and electronic properties of self-assembled nanostructures on silicon surfaces. He also worked at Hitachi, Japan and at the Paul Scherrer Institute, Switzerland. In 2009, he joined EPFL's PV-Lab, Switzerland as a postdoc and project leader where he works on advanced light management concepts for thin-film silicon solar cells ranging from the development of new substrates and electrode materials to the fabrication and characterization of complete cells.
[1] M. Despeisse et al, Appl. Phys. Lett. (2010)
[2] P. Cuony et al, Appl. Phys. Lett. (2010)
[3] M. Despeisse et al, Phys. Stat. Solidi a (2011)
[4] S. Benagli et al, Proc. 24th European Photovoltaic Energy Conference, Hamburg (2009)
[5] J. Bailat et al, Proc. 5th World Conference on Photovoltaic Energy Conversion, Valencia (2010)
[6] C. Battaglia et al, Appl. Phys. Lett. (2010)
[7] C. Battaglia et al, Nano Letters (2011)
[8] C. Battaglia et al, submitted (2011)
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