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.