Low-resistance earth-abundant metal contacts to nitrogen-doped cuprous oxide thin films

Formation of low-resistance ohmic contacts to novel earth abundant absorber materials is required to minimize resistive power losses in photovoltaic devices. We first show that the specific contact resistivity (ρ_c) of 3 inert metals (Au, Ag and Pd) to copper (I) oxide (Cu₂O) thin films can be reduced significantly through the application of a doped Cu₂O functional layer. Specific contact resistivity as low as 1.1×10^-4 Ω·cm² is observed for Pd to nitrogen-doped (N-doped) Cu₂O films. This is the lowest-ever reported ρ_c to date for Cu₂O films. Temperature-dependent current-voltage (IVT) measurements indicate that thermionic emission dominates for nominally undoped films whilst field emission dominates for N-doped films. Additionally, IVT suggests that ρ_c does not depend on metal type for N-doped films due to the formation of a tunneling junction. Lastly, we demonstrate that low contact resistivity can be achieved on N-doped Cu₂O films using Earth-abundant metals such as Cu and Ni.