Yao Jianxi

Ag nanoparticles preparation and their light trapping performance

Ag nanoparticles were fabricated on Si substrates by radio-frequency magnetron sputtering and thermal annealing treatments. It was found that Ag nanoparticles are ellipsoid at low annealing temperature, but the axis ratio decreases with the increase of annealing temperature, and a shape transformation from ellipsoid to sphere occurs when the temperature increases to a critical point. The experimental results showed that the surface plasmon resonances depend greatly on the nanoparticles’shape and size, which is in accordance with the theoretical calculation based on discrete dipole approximation. The results of forward-scattering efficiency (FSE) and light trapping spectrum (LTS) showed that Ag nanoparticles annealed at 400°C could strongly enhance the light harvest than those annealed at 300 and 500°C, and that the LTS peak intensity of the former is 1.7 and 1.5 times stronger than those of the later two samples, respectively. The conclusions obtained in this paper showed that Ag ellipsoid nanoparticles with appropriate size is more favorable for enhancing the light trapping.

Dipolar and Quadrupolar Modes of SiO2/Au Nanoshell Enhanced Light Trapping in Thin Film Solar Cells

Dipolar and quadrupolar resonance wavelengths of SiO2/Au nanoshell surface plasmons are designed at 560 nm to enhance the light trapping in thin film solar cells. In order to quantitatively describe the light trapping effect, the forward-scattering efficiency (FSE) and the light trapping efficiency (LTE) are proposed by considering the light scattering direction of SiO2/Au nanoshells. Based on the Mie theory, the FSE and the LTE are calculated for SiO2/Au nanoshells of different dimensions, and the contributions of the dipolar and quadrupolar modes to the light trapping effect are analyzed in detail. When the surface coverage of nanoshells is 5%, the LTEs are 21.7% and 46.9% for SiO2/Au nanoshells with sizes of (31 nm, 69 nm) and (53 nm, 141 nm), respectively. The results indicate that the SiO2/Au nanoshell whose quadrupolar mode peak is designed to the strongest solar energy flux density of the solar spectrum facilitates the further enhancement of light harvesting in thin film solar cells.