Resistivity transients in solution‐processed transparent ZnO thin films as a function of UV illumination wavelength

Abstract

Transparent conductive zinc oxide thin films are deposited by chemical bath deposition (CBD) followed by exposure to UV‐visible light to increase their electrical conductivity. Selected spectral bandwidths are filtered from a Hg(Xe) lamp in the range of 280–546 nm to investigate resistivity transients as a function of the illumination wavelength. The conductivity increases by a factor of ∼103 for illumination wavelengths shorter than the fundamental absorption edge, as predicted by the ionized oxygen species adsorption model. If the thin film thickness exceeds the UV radiation penetration depth significantly (≳1 µm), the conductivity can most effectively be increased by exposing the films to wavelengths situated in the Urbach tail at ∼365 nm as both, absorptance and transmittance lie above 20%, enabling the radiation to penetrate the whole layer, while still locally generating enough electron‐hole pairs for the desorption of chemisorbed species.