Pulsed-laser hyperdoping and surface texturing for photovoltaics

We describe two ways in which pulsed lasers can be used to increase efficiency in photovoltaic devices. First, pulsed-laser hyperdoping can introduce dopants into a semiconductor at non-equilibrium concentrations, which creates an intermediate band in the bandgap of the material and modifies the absorption coefficient. Second, pulsed-laser irradiation can enhance geometric light trapping by increasing surface roughness. Hyperdoping in silicon enables absorption of photons to wavelengths of at least 2.5 mu m, while texturing enhances the absorptance to near unity at all absorbing wavelengths. This article reviews both effects and comments on outstanding questions and challenges in applying each to increasing the efficiency of photovoltaic devices.