Third-generation approaches to photovoltaics (PVs) aim to achieve high-efficiency devices but still use thin-film, second-generation deposition methods. The concept is to do this with only a small increase in areal costs and hence reduce the cost per Watt peak 1 (this metric is the most widely used in the PV industry). Also, in common with Si-based, second-generation, thin-film technologies, these will use materials that are both nontoxic and not limited in abundance. Thus, these third-generation technologies will be compatible with large-scale implementation of PVs. The approach differs from first-generation fabrication of high-quality, low-defect, single-crystal PV devices that have high efficiencies approaching the limiting efficiencies for single-bandgap devices but use energy- and time-intensive techniques.