Pigmented materials for light trapping in thin-film polycrystalline silicon solar cells.

摘要

Sunlight is an ideal, yet largely untapped, energy resource. Photovoltaics are well suited to harness this energy supply if the cost and efficiency goals necessary for competition with conventional electricity supplies can be reached. Thin-film polycrystalline silicon solar cells have many advantages, making them a good candidate to achieve these goals.; This technology has several significant technological challenges, however, one of which is overcoming the relatively weak absorption of light by the thin silicon layer. This work proposes, analyzes and demonstrates a novel method of achieving a significant degree of optical confinement. Specifically, pigmented materials are used at the back surface of the thin silicon solar cell to reflect light back into the silicon layer with a diffuse pattern. If the appropriate materials are chosen for the back reflector, a large fraction of light can be reflected at the front surface by total internal reflection, and a high degree of optical confinement is possible.; The science and technology of pigmented materials and silicon solar cells are well developed. This dissertation bridges the two with a new optical model. A discrete four-flux approach is used to model the optical fluxes at each surface of the silicon solar cell.; Three experiments are designed to verify the model. Pigmented materials are fabricated and characterized. They are then applied to the back of thin layers of silicon and the total front-surface reflectivity is predicted and measured, with good agreement. Finally, thin silicon solar cells are fabricated and the pigmented materials are applied to the back surface. The external quantum efficiency of the solar cells is measured. The model is then used. in combination with a widely used solar cell simulation software package, to predict the external quantum efficiency, with good agreement.