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Cu 2 O p-n homojunction solar cells were fabricated by the consecutive electrochemical deposition of p-Cu 2 O layer, followed by n-Cu 2 O layer. The surface morphology of p-type Cu 2 O, which determines the p-n junction interface, was modified to investigate its effect on the performance of the homojunction solar cell. The results showed that the junction quality and the cell efficiency varied significantly depending on the crystals faces exposed at the p-n junction, although the resistivity of the p-and n-layers remained comparable. The best performance of the homojunction cell fabricated in this study was V OC = 0.423 V, I SC = 2.5 mA/ cm 2 , fill factor (ff) = 27%, and η = 0.29%. The main limiting factor for the cell efficiency was the high resistivity of both p-and n-layers. Doping studies and finetuning of the junction morphology will be necessary to improve the performance of the Cu 2 O homojunction solar cells further.

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An intermediate of the dark reductive reaction of n-TiO2 with an aqueous electrolyte was identified. This intermediate forms surface states on the semiconductor. The energy and surface concentration of these states were evaluated by impedance measurements. We report on sub-bandgap photoresponse due to excitation of electrons from the valence band to these states. The potential-photocurrent behavior of these states is unique and is being fully accounted for by the proposed mechanism of their dynamic formation and annihilation. * Electrochemical Society Active Member. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-28 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-28 to IP

In this Letter, we report the effects of ammonium sulfide [(NH4)2S] surface treatment on electrical and optical characteristics of the electrodeposited n‐type Cu2O thin films on Ti substrates. Films characterized structurally and morphologically before and after the surface treatment were compared using conductivity, spectral photoresponse and current–voltage (I–V) measurements. The ammonium sulfide surface treatment time showed an impact on optical and electrical characteristics of the films. Treated Cu2O films exhibited enhanced conductivity giving rise to a 50‐fold increase in the photocurrent and improved I–V characteristics. It was found that the sulfur passivation resulted in a nearly ohmic behaviour for Au or Ni contacts made with n‐type Cu2O whereas Ag or Cu contacts showed nearly Schottky behaviour. The results showed that ammonium sulfide treatments were very effective to passivate defects and improve the optical and electrical properties of polycrystalline n‐type Cu2O thin films that may provide a solid platform for Cu2O based devices of enhanced quality. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)