Tiny rods to harness solar energy
doi:10.1038/nindia.2010.85 Published online 22 June 2010
Researchers have designed a new type of organic photovoltaic (OPV) cell that uses nano-sized rods of copper phthalocyanine (CuPc), a copper-based organic compound. This easy-to-produce OPV cell may open up a new route towards harnessing solar energy.
OPV cells are cheap, lightweight and mechanically flexibility, making them suitable as efficient solar cells. However, so far controlled nanostructure-based OPV cells have not been widely used as solar cells.
To make a nanostructured heterojunction-type solar cell, the researchers laid a 50-nm-thick CuPc film on a pre-cleaned patterned glass substrate coated with indium tin oxide and then covered with a polymer layer. They applied different organic solvents — chlorobenzene, toluene and acetone — to the surface of the CuPc film, allowing the solvents to evaporate at room temperature and thus leaving nanorods of different shapes and sizes.
Treatment with chlorobenzene created nanorods with diameters of 15–35 nm and lengths of 100-200 nm, toluene treatment gave nanorods with diameters of 30–35 nm and lengths of 200–400 nm, and acetone treatment resulted in highly dense standing nanorods with diameters of ~40–60 nm.
A fullerene-based electron acceptor layer was smeared on top of the CuPc nanorods, following which a 10-nm-thick electron transporting layer and aluminium top electrode strip were also deposited.
"Nanostructure-level tailoring of CuPc molecules resulted in more than a twofold improvement in device performance over conventional bi-layer solar cells," says lead researcher Achintya Dhar.
- Karak, S. et al. Improvement of efficiency in solar cells based on vertically grown copper phthalocyanine nanorods. J. Phys. D 43, 245101 (2010) | Article