Efficient photovoltage multiplication in carbon nanotubes

• DOI: 10.1038/nphoton.2011.250
• Publication Date: 2011-10-07T19:13:02Z
• Authors: Leijing Yang; Sheng Wang; Qingsheng Zeng; Zhiyong Zhang; Tian Pei; Yan Li; Lian-Mao Peng
• Keywords: Multiple exciton generation; Ohmic contact; Carbon fibers

Carbon nanotubes are direct-bandgap materials that are not only useful for nanoelectronic applications1,2, but also have the potential to make a significant impact on the next generation of photovoltaic technology3,4,5. A semiconducting single-walled carbon nanotube (SWCNT) has an unusual band structure, as a result of which high-efficiency carrier multiplication effects have been predicted and observed6,7 and films of SWCNTs with absorption close to 100% have been reported8. Other features that are also important for photovoltaic applications include high mobility9,10 and the availability of ohmic contacts for both electrons11,12 and holes13. However, the photovoltage generated from a typical semiconducting SWCNT is less than 0.2 V, which is too small for most practical photovoltaic applications. Here, we show that this value may be readily multiplied by using virtual contacts at the carbon nanotube. In one example, more than 1.0 V is generated from a 10-μm-long carbon nanotube with a single-cell photovoltage of ∼0.2 V. Photovoltages generated from semiconducting single-walled carbon nanotubes are often too small for most practical solar-energy-harvesting applications. Here, researchers demonstrate that virtual contacts can be used to multiply photovoltages from around 0.2 V to 1.0 V.