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

Abstract

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 (Cu 2 O) thin films can be reduced significantly through the application of a doped Cu 2 O functional layer. Specific contact resistivity as low as 1.1×10−4 Ω·cm2 is observed for Pd to nitrogen-doped (N-doped) Cu 2 O films. This is the lowest-ever reported ρ c to date for Cu 2 O 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 Cu 2 O films using Earth-abundant metals such as Cu and Ni.