Jul 27, 2012
Air-assisted fabrication paves the way for low-cost graphene solar cells
Using a simple air-assisted fabrication process, researchers from the Small Systems Laboratory at the University of Louisville, US, have demonstrated large, position-dependent, near-infrared (NIR)-induced photocurrents in single layer graphene (SLG) assemblies. Position-dependent photocurrents exhibited an increase when the positive electrode was illuminated, a decrease when the negative electrode was illuminated, and a negligible response when the area between the electrodes was illuminated.
In the study, NIR-induced photocurrent increases in excess of 1800% of dark current were obtained (335 mW NIR illumination). Such large responses result from built-in electric fields and optically generated temperature gradients. These low-density thin films not only exhibited interesting morphology, but also demonstrated classic Haynes-Shockley characteristics of drift and diffusion.
Fabrication of these SLG macroscopic thin films using air-assisted deposition is straightforward, does not require lithographic patterning, and produces devices with reliable and repeatable photocurrent responses. Large photocurrents in lithography-free SLG assemblies could help enable low-cost solar cells. The work also assists the development of grapheme-based p-n junction photodetectors, and infrared bolometers.
The simple shadow/spray masking for gold/graphene deposition could be of interest in astronomy, telecommunication and imaging applications. Finally, demonstration of Haynes-Shockley experiments in graphene thin films could serve as an educational tool for future young scientists and engineers.
The researchers presented their results in the journal Nanotechnology.
About the author
The study was conducted in the Small Systems Laboratory at the University of Louisville in Louisville, Kentucky. Funding for this research was partially supported by NSF CAREER award ECCS: 0853066 and NSF award ECCS: 1202190 for one of the authors (B.P.). James Loomis is a PhD candidate in mechanical engineering. Dr Balaji Panchapakesan is a professor at the University of Louisville and director of the Small Systems Laboratory.