Multi-wall carbon nanotube coating of fluorine-doped tin oxide as an electrode surface modifier for polymer solar cells

• Published in: Solar energy materials and solar cells 2014-03, Vol.122, p.297-302
• Main Authors: Capasso, A., Salamandra, L., Chou, A., Di Carlo, A., Motta, N.
• Format: Article
• Language: English
• Subjects: Applied sciences; Carbon nanotubes; Chemical vapor deposition; Density; Electrodes; Energy; Exact sciences and technology; Multi wall carbon nanotubes; Nanostructure; Natural energy; Organic photovoltaics; Photovoltaic cells; Photovoltaic conversion; Polymer solar cells; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Surface modifier; Tin oxides; Transparent conductive oxide
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2013.10.022

A controlled layer of multi-wall carbon nanotubes (MWCNT) was grown directly on top of fluorine-doped tin oxide (FTO) glass electrodes as a surface modifier for improving the performance of polymer solar cells. By using low-temperature chemical vapor deposition with short synthesis times, very short MWCNTs were grown, these uniformly decorating the FTO surface. The chemical vapor deposition parameters were carefully refined to balance the tube size and density, while minimizing the decrease in conductivity and light harvesting of the electrode. As created FTO/CNT electrodes were applied to bulk-heterojunction polymer solar cells, both in direct and inverted architecture. Thanks to the inclusion of MWCNT and the consequent nano-structuring of the electrode surface, we observe an increase in external quantum efficiency in the wavelength range from 550 to 650nm. Overall, polymer solar cells realized with these FTO/CNT electrodes attain power conversion efficiency higher than 2%, outclassing reference cells based on standard FTO electrodes. •Multi-walled carbon nanotubes are grown on the surface of fluorine-doped tin oxide (FTO) electrodes by chemical vapor deposition.•Low-temperature (up to 600°C) synthesis of carbon nanotubes does not alter the capability of FTO electrodes but rather improves their electric behavior.•Polymer solar cells with direct and inverted architecture are successfully built and tested with FTO/CNT electrodes.•The carbon nanotube coating on FTO is found to significantly increase the external quantum efficiency of polymer cells.•The higher work function attained by CNT-modified electrodes is beneficial for the energy band alignment of polymer cells in direct architecture.