By Will Soutter
A research team from the University of Florida (UF) has fabricated a graphene solar cell that demonstrates a power conversion efficiency of 8.6%, a record value, when considering earlier attempts in the making of graphene solar cells that managed only 2.9% conversion efficiency.
The study findings have been reported online in Nano Letters. The research team used trifluoromethanesulfonyl-amide (TSFA) for doping the graphene film used in the fabrication of the solar cell.
Xiaochang Miao, one of the researchers, explained that the addition of TSFA increases the conductivity of the graphene film and raises the electric field potential within the cell, which in turn increases the power conversion efficiency of the cell. The effects of TSFA are durable as it has higher stability than earlier dopants. Moreover, the technique is simple and inexpensive.
The solar cell developed by the research team resembles a 5-mm-square window that has a gold casing. The window is a silicon wafer coated with a graphene monolayer. When it comes into contact, silicon and graphene create a Schottky junction, which is a one-way path for electrons and operates as a power conversion region for solar cells when light illuminated on it.
Schottky junctions are usually created by applying a metal layer over a semiconductor. However, in 2011, scientists at the UF Nanoscience Institute for Medical and Engineering Technologies found that graphene can be used as a replacement for metal forming the junction.
The research team’s solar cell prototype was fabricated on a rigid silicon base, which is not an affordable choice for volume production. Co-author Arthur Hebard senses the possibilities for integrating the doped graphene with low-cost flexible substrates such as polymer sheets.