Abstract: The high cost of high-conductivity transparent conductors made from indium tin oxide (ITO) is a significant barrier to the commercialization of solution-processed solar cells and OLEDs. This talk will focus on the development of copper nanowires as a solution-coatable alternative to ITO. Copper nanowires can be produced with a scalable, solution-based process in which they grow at ~100 nm/s through the diffusion-limited addition of a copper(I) precursor to a copper nanoparticle. Maximizing the optical transmittance of a nanowire film while minimizing its electrical resistance requires minimizing the diameter of the nanowires, area fraction of the nanowires, the number of contacts between nanowires, and the contact resistance between nanowires. Minimization of diameter, area fraction, and number of contacts was achieved by development of a synthesis that produces copper nanowires with aspect ratios as high as 5700 in 30 min. The contact resistance between copper nanowires is initially high due to the presence of a native oxide; this oxide can be eliminated by dipping the nanowires in acetic acid. Subsequent oxidation of copper nanowires can be prevented by coating them with a thin layer of Ni, Zn, Sn, In, or Ag. Organic solar cells made with copper-based nanowires exhibit device efficiencies of 5%, comparable to values obtained for devices made with silver nanowire-based transparent electrodes. Recent applications of copper-based nanowires to water splitting and non-volatile information storage will also be briefly discussed.