Abstract:
We present a stable inkjet printable graphene ink, formulated in isopropyl alcohol via liquid phase
exfoliation of chemically pristine graphite with a polymer stabilizer. The rheology and low deposition
temperature of the ink allow uniform printing. We use the graphene ink to fabricate counter electrodes
(CE) for natural and ruthenium-based dye-sensitized solar cells (DSSCs). The repeatability of the printing
process for the CEs is demonstrated through an array of inkjet-printed graphene electrodes, with ~5%
standard deviation in the sheet resistance. As photosensitizers, we investigate natural tropical dye extracts
from Pennisetum glaucum, Hibiscus sabdariffa and Caesalpinia pulcherrima. Among the three natural
dyes, we find extracts from C. pulcherrima exhibit the best performance, with ~0.9% conversion efficiency
using a printed graphene CE and a comparable ~1.1% efficiency using a platinum (Pt) CE. When used with
N719 dye, the inkjet-printed graphene CE shows a ~3.0% conversion efficiency, compared to ~4.4% obtained
using Pt CEs. Our results show that inkjet printable graphene inks, without any chemical functionalization,
offers a flexible and scalable fabrication route, with a material cost of only ~2.7% of the
equivalent solution processed Pt-based electrodes.
