ICT2014 Abstracts

Single wall carbon nanotube (SWCNT) has been receiving an interest of research for solar cell applications. Due to its simple lattice structure, the photon absorption spectrum is quite selective for wavelength. The wavelength at higher absorption observes to be dependent to the diameter and chirality of SWCNTs. The potential of solar harvesting was reported in a study with carbon nanotubes in literature. If the heat source is a combustion frames or hot gas instead of sun, the spectrum peak is found at longer wavelength. Since the primary peak absorption wavelength of the SWCNT is the range of near infrared to infrared, SWCNT absorber will work more effective for such radiation heat source rather than the solar spectrum.

We assume one photon exchanges energy with one exciton. The energy level of the excitons namely hot carriers depends on that of the incoming photons, which is determined by the peak spectrum of the radiation by following Wien’s displacement law. For example, 26.7% of higher energy level photons are incoming over the peak wavelength (equivalent to 0.6 eV) from the heat source at the temperature 1400 K by Planck’s law, where a specific SWCNT absorbs the wavelength.

Since the SWCNT is optically selective, the design of reflective filters which prevents the gray body heat radiation loss at longer wavelength from the absorber could be reasonably easier.

A P-N junction structure will be presented as a simplest case. The open voltage will be 0.5~ 1 Volts. Assuming parasitic losses are reasonably small and external load is ideal for SWCNT, the extracted power could be few micro Watts per SWCNT with 1 MW/m² of incoming energy flux. The SWCNT density 10⁺⁸~10⁺⁹ 1/cm² of forest approximately matches the power density. The internal Joule heat will easily dissipate to a heat sink with large thermal conductivity.