UC San Diego

Silver nanoparticles (AgNPs) have been investigated for many years now due to their exceptionally strong absorption and scattering of light and to their antimicrobial capabilities. These properties are the basis of many applications such as chemical sensors, Surface-enhanced Raman Spectroscopy, antimicrobial textiles, and medical devices with sterilized surfaces. AgNPs have also been added to solar cells to enhance the photoefficiency. Thus far the results have been mostly unsuccessful. For this reason, the purpose of this project was to try a new approach to adding AgNPs to enhance the efficiency of solar cells in which the AgNPs are separated from the surface by distances on the order of 1nm, and they have a size and shape such that they absorb and scatter light in the red and near-infrared (near-IR) regions where the absorption by solar cells is low. Experimental results of the work are presented in which the efficiency of bare thin silicon solar cells was modestly increased by about 1%. These results prove a proof of concept that can lead to further explorations. Computer simulations that use the discrete dipole approximation (DDA) were also carried out to provide theoretical guidance to the experiments. In separate work the DDA was used to simulate the UV-Visible/ near-IR extinction spectra of the AgNPs that were synthesized in solution for the solar cell project. The solution phase simulations along with Transmission Electron Microscopy (TEM) images of the AgNPs provided a cross check of the origins of the structure in the experimental UV-Visible/ near-IR spectrum.