Photo-to-electricity generation of aligned carbon nanotubes in water

The photovoltaic effect occurs at the interface between two different types of semiconductors that are joined together to create a p-n junction, and it has been explored as a basic principle to harvest solar energy to generate electricity. The active materials are typically protected from water for stable performances, and the photovoltaic effect is observed in photovoltaic materials with appropriate energy bands and interfaces. Here we have discovered another new and general photo-to-electricity phenomenon in semiconducting materials in water. The photo-to-electricity conversion could be realized by using the identical type of semiconductor as the active material. Aligned carbon nanotube sheets were demonstrated to output high open-circuit voltages up to 0.48 V. Due to the intrinsic flexibility of the designed carbon nanotube sheets, the output voltage could be well maintained after deforming for 8000 cycles.