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.