Efficient Organic Excitonic Solar Cells with Carbon Nanotubes Replacing In2O3:Sn as the Transparent Electrode

We report two organic excitonic solar cell structures with the conventional ITO anode replaced by a thin single-walled carbon nanotube (SWCNT) layer. The first structure, SWCNT/PEDOT/P3HT:PCBM/Al, gave a non-optimized device efficiency of 2.61%, which is competitive with ITO-based devices. The second, SWCNT/P3HT:PCBM/Al, is unique, as it did not use PEDOT as a hole selective contact. This had a promising efficiency of 1.43%. The open structure of the SWCNT network, and its inherent compatibility with the chlorobenzene solvent used to deposit the P3HT:PCBM, allow for intimate intermixing with the active layers of the device and the elimination of PEDOT. The strong rectifying behavior of the device shows that nanotubes are selective for holes and are not recombination sites in the active layer of the device. This excitonic solar cell is the first measurably efficient organic device produced without ITO and PEDOT