Tailoring optical and electrical properties of carbon nanotube networks for photovoltaic applications

Maximizing the electrical conductivity and optical transmittance of a carbon nanotube (CNT) network is critical for using CNTs as electrodes of solar cells. In this paper, the effect of CNT network morphology on its electrical and optical properties is investigated both experimentally and theoretically, indicating that a network consisting of loosely-percolated small long nanotube bundles or individual CNTs showed outstanding transparency and electrical conductivity. Further removal of surfactant absorbed onto the CNTs or treating them with nitric acid significantly increased the electrical conductivity of CNT films without sacrificing the transparency. The optimized CNT network demonstrated a surface resistivity of 205 ohm/square with 65% optical transmittance. These results will significantly facilitate the application of CNTs in solar cells and other electronic devices.