Crown-ether cyanide treatment, which simply involves immersion in KCN solutions containing 18-crown-6 followed by rinse, is studied in relation to electrical and optical properties of nitrogen-doped, polycrystalline Cu2O thin films, and its effect is compared with that of hydrogen treatment. By the crown-ether cyanide treatment, the luminescence intensity due to the near-band-edge emission of Cu2O at around 680 nm is enhanced, and the hole density is increased from the order of 1016 to 1017 cm−3, analogous to hydrogen treatment. The effects of the passivation by the hydrogen treatment completely disappear after annealing at 350 °C, while those of the crown-ether cyanide treatment stay unchanged after the same annealing treatment. From these results, the crown-ether cyanide treatment for polycrystalline Cu2O thin films can be concluded to be a more suitable method of passivating defects than the hydrogen treatment.

PACS 73.61. Ga, 81.15.Cd, 84.60.Jt Polycrystalline n-ZnO/p-Cu 2 O heterojunctions were fabricated by reactive sputtering for photovoltaic applications. Although electrical rectification was not reproducibly obtained in the as-grown samples, rectification was observed in the samples fabricated with cyanide treated Cu 2 O. We have previously shown that cyanide treatment has an effective role in passivation of defects in Cu 2 O, in analogy to hydrogen passivation. It is, therefore, believed that the observed improvement in the electrical rectification of the ZnO/Cu 2 O heterojunctions is attributable to the defect passivation near the hetero-interface. The effectiveness of the cyanide treatment and the importance of defect passivation in ZnO/Cu 2 O heterojunctions are presented.

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