Study On Board-band Spectrum Metal Nanostructures Based On Discrete Dipole Approximation

To explore metal nanostructure or composite structure particles which can improve the efficiency of solar energy conversion and have wide-band spectrum properties, or particles with adjustment of the localized surface plasmon resonance properties, we analyze the optical properties of four different metal nanostructure particles, such as metals gold, silver, copper and magnetic material cobalt using the discrete dipole approximation method. We detailedly study the extinction spectra of the metal, alloy, core-shell structure and hollow structure nanoparticles, and discuss the factors such as the specific structure and components that influence the surface plasmon resonance properties of the materials. The obtained results are as follows:The silver nanoparticles with radius of 50 nm which are dispersed in phenolic resin medium have a broad-band scattering spectra in the visible light region. The gold nanoparticles with radius of 70 nm have the extinction spectra which can span the visible region. For copper nanoparticle with radius 90 nm, it has the similar property. These nanoparticles can be applied into many fields, such as the solar cells, which increase the efficiency of utilization of visible light, and improve the photoelectric conversion efficiency of the device. For silver-gold alloy, copper-gold alloy, silver-copper alloy and silver-gold core-shell structure nanoparticles, they have different optical properties. The extinction peak position of these structures can be tuned from 480 nm to 580 nm, 580 nm to 630 nm, 480 nm to 600 nm, 400 nm to 560 nm, respectively. The extinction peak position of hollow gold nanoparticles can be adjusted within 600 nm-900 nm, and it can be shifted from visible light wavelength to infrared area when the core radius and shell thickness of hollow particle is changed. These results have unique advantages in improving the energy absorption of the specific light spectrum in solar cell field.The extinction spectra of cobalt metal nanoparticles can shift from ultraviolet to visible light area with increasing the radius from 30 nm to 70 nm, which its peak position is changed from 325 nm to 585 nm. The cobalt nanoparticle with 50 nm radius has the maximal extinction efficiency; moreover the scattering efficiency excels its absorption. It can be suitable for application of the solar cell. The hollow cobalt nanoparticle has the maximal efficiency spectrum located at the visible region when the inner radius equals to 40 nm and the shell thickness is 5 nm. The cobalt-gold alloy with atom ratio 1 has a broad scattering spectrum in the range of visible region. These results can also provide some suggestion for choosing the structural parameters in practical application, such as solar energy field.