Graphene and the Future of Photovoltaic Technology

Clara Druzgalski
December 3, 2011

Submitted as coursework for PH240, Stanford University, Fall 2011

Graphene and the Future of Solar Energy

Graphene is a recently isolated form of carbon whose structure consists of a one-atom-thick layer of carbon atoms bonded in the shape of a honeycomb. Graphene has a number of unique properties that are not typically associated with other forms of carbon such as: optical transparency, flexibility, and high conductivity. [1] These properties make graphene a very attractive material for use in the next generation of faster microchips, ultracapacitors with greater storage densities and solar cells. [2,3] For solar cells, graphene would be an ideal material for use as the transparent conducting electrode component which contributes a significant cost to the overall price tag of photovoltaic devices.

Currently, many photovoltaic devices use a substance called indium tin oxide (ITO) for the transparent conducting electrode layer. ITO is a limiting factor preventing a widespread adoption of solar cells as the popularity of indium-containing consumer products such as liquid crystal displays and touch screens has fueled a dramatic price increase of indium. [4] Indium is a relatively rare metal and thus we are limited by the mining capacity of known indium deposits, and subject to price volatility according to demand in the market. In addition to cost, the brittleness of ITO prevents solar cells from taking new, flexible forms that would increase their range of application. Graphene has the advantageous combination of transparency, flexibility and conductivity which makes it an ideal replacement for indium tin oxide (ITO) as a transparent conducting electrode.

Although graphene seems like an ideal fit to make flexible solar cells, while no longer being constrained by the price volatility of indium, graphene itself is such a new material that currently no method of large scale production is in place. Since the base material of graphene is carbon, an extremely abundant, inexpensive resource, it is reasonable to expect that a low cost manufacturing strategy for graphene will eventually materialize. Currently, isolation of graphene takes place on a small scale at specialized laboratories and while several techniques for graphene production have been reported, quality, scalability, and cost have prevented these techniques from being adopted as a large-scale solution. For example, exfoliation of graphite is more cost effective than other techniques, but is limited by its small size, usually less than 1000 μm2. [5] Reduction of graphite oxide (GO) to form graphene is only able to reduce the outer surface of GO, leaving the remainder of the material an insulator rather than a conductor. Another method of GO reduction using high temperatures is incompatible with the flexible substrates that would allow solar cells to take new forms. [6,7] One of the more promising methods of solving scalability and quality issues is graphene production by chemical vapor deposition (CVD), yet the issue of how to transfer a one-atom-thick sheet of graphene without damaging it continues to plague this technique. [8]

Fortunately, the highly desirable properties of graphene have prompted a surge of research into this material, with many breakthroughs occurring every year. This material has captured the attention of the scientific community to such a degree that the 2010 Nobel Prize in physics was awarded to a group of scientists for their experiments with graphene. [9] With new production techniques being reported frequently, along with the continual refinement of more mature techniques, it seems that it is only a matter of time before this material can be practically adopted in industry for use in consumer goods.

© Clara Druzgalski. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] A. K. Geim and K. S. Novoselov. "The Rise of Graphene," Nature Mat. 6, 183 (2007).

[2] M. Stoller et al., "Graphene-Based Ultracapacitors," Nano Lett. 8, 3498 (2008).

[3] J. Wu et al., "Organic Solar Cells with Solution-Processed Graphene Transparent Electrodes," Appl. Phys. Lett. 92, 263302 (2008).

[4] B. G. Lewis and D. C. Paine, "Applications and Processing of Transparent Conducting Oxides," Mat. Res. Soc. Bull. 25, 22 (2000).

[5] C. Berger et al., "Electronic Confinement and Coherence in Patterened Epitaxial Graphene," Science 312, 1191 (2006).

[6] X. Li et al., "Highly Conducting Graphene Sheets and Languir-Blodgett Films," Nature Nanotechnol. 3, 538 (2008).

[7] G. Eda, G. Fanchini and M. Chhowalla, "Large-Area Ultrathin Films of Reduced Graphene Oxide as a Transparent and Flexible Electronic Material," Nature Nanotechnol. 3, 270 (2008).

[8] X. Li et al., "Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils," Science 324, 1312 (2009).

[9] A. Cho, "Still in Its Infancy, Two-Dimensional Crystal Claims Prize," Science 330, 159 (2010).

[10] Image courtesy of United States Air Force.