Research On Optical And Electrical Properties Of Carbon Nanotubes Based Phtovoltaic

The band structure of the single walled carbon nanotubes is a crucial factor, the single walled carbon nanotubes as the basic unit of nan-electronic device, including photovoltaic device. Therefore, the electronic structure and band gap of carbon nanotubes have become a research focus of condensed matter physics and nanomaterial. Specifically, the application of carbon nanotubes in the photovoltaic field is still in its infancy, enormous research efforts are required to promote the practical application of CNTs in solar cells.At present, many investigators have studied the electronic structure and band gap of single walled carbon nanotubes and predicted their electrical and optical properties. However, both band structures and optical properties of CNTs are for single carbon, based on first principle and finite element method respectively. It is difficult to achieve in the actual processing.Electronic band structures and density of states and optical properties of single-walled carbon nanotubes (SWNTs) (7,0), (8,0), (9,0), (10,0), (11,0), (12,0), (13,0), (5,1), (4,2), (4,3) were studied using first principles ultrasoft pseudopotential with plane wave basis with CASTEP(Cambridge Sequential Total Energy Package). The results shows that the single-walled carbon nanotube is semiconductor with direct band gap that is not simple linear relationship with the diameter of tubes; The magnitude of the peaks in imaginary part spectrum of dielectric function depends on the direction of electric field and the parameters of tubes, and the peaks distributes in regions of 200～2000nm importantly; The work-function of single-walled carbon nanotube exhibits randomness compared with diameter of tubes and distributes in 4.3～5.0eV.Properties of absorbed power of the single-walled carbon nanotube bundles were calculated using RF module of Comsol Multiphysics based on the Finite-Element-Method formulation of Maxwell’s equations. The single-walled carbon nanotube bundles were set as solid cylinders. Changing the diameter and distance of carbon nanotube bundles and wavelength of the incident electromagnetic wave to study the optical performance of single walled carbon nanotube bundles of (8,0), (10,0), (11,0), (5,1), (4,2), (4,3) in the THz frequency range. The results shows that there is a strong influence of electromagnetic wave of all bundles and absorbed power in special diameter of bundles, that to say, there is a best value of diameter of bundles to fabricate Photovoltaic device. In addition, the conversion efficiency of PV cells were solved, the value are 34.07%,33.4%,37.26%,31,49%,31.38%,32.28%, this result shows that the different structure of carbon nanotube bundles have different characteristic of PV in regions of 200～1000nm. Combining the distribution of solar energy, the carbon nanotube bundle (11,0) have the best PV characteristic.