Femtosecond laser texturing of silicon yields micrometer scale surface roughness that reduces reflection and enhances light absorption. In this work, we study the potential of using this technique to improve efficiencies of amorphous silicon-based solar cells by laser texturing thin amorphous silicon films. We use a Ti:Sapphire femtosecond laser system to texture amorphous silicon, and we also study the effect of laser texturing the substrate before depositing amorphous silicon. We report on the material properties including surface morphology, light absorption, crystallinity, as well as solar cell efficiencies before and after laser texturing.
We have developed a technique, optical hyperdoping, for doping semiconductors to unusually high levels and endowing
them with remarkable optoelectronic properties. By irradiating silicon (Si) with a train of femtosecond laser pulses in the
presence of heavy chalcogen (sulfur, selenium, and tellurium) compounds, a 100-300 nm thin layer of Si is doped to nonequilibrium
levels (~1 at. %). Hyperdoped silicon exhibits near-unity photon absorptance from the ultraviolet (λ < 0.25
μm) to the mid-infrared (λ > 2.5 μm), even though crystalline silicon is normally transparent to wavelengths λ > 1.1 μm
due to its band gap at 1.1 eV. Concurrent to doping, we are also able to use fs-laser irradiation to create light-trapping
surface textures on the micro- and nanometer scales. Together, optical hyperdoping and surface texturing represent a
route towards high-performance thin film photovoltaic devices.