Dan Trivich

Photoelectric properties of cuprous oxide

The effects of transient and steady−state illumination on the electrical properties of single−crystal cuprous oxide have been investigated in the temperature range from 230 to −20 °C. For samples equilibrated well within the region of Cu2O stability, conduction was governed by an acceptor level at 0.4 eV above the valence band as determined from the temperature dependence of the Hall effect. The presence of two minority carrier trapping levels was also established and trapping parameters were determined from an analysis of the transient photoconductivity. The 0.4−eV acceptor level was also found to be present in a sample equilibrated under conditions placing its composition in a region near the CuO−Cu2O phase boundary. For this sample, however, only a single deeper trapping level was observed. A third type of sample, equilibrated under conditions which placed its composition in a region near the Cu−Cu2O phase boundary, was characterized by both a high hole density and a high mobility with an acceptor leve...

Heterojunction solar cells on cuprous oxide

Abstract Heterojunction solar cells were made on Cu2O by sputtering In2O3, SnO2, CdO and mixtures of CdO and SnO2 and by thermal evaporation of ZnSe. Photovoltaic effects were observed in most cases. High series resistances were an indication of chemical reactions at the interface. Auger surface analysis showed evidence of copper metal at the interface, arising from chemical reactions. For a CdO/Cu2O junction formed at room temperature, no copper metal was found at the interface. The CdO/Cu2O cells showed V oc = 0.4 V and I sc = 2 mA cm −2 . The properties appear to be dominated by a multiple-step tunneling at the junction, presumably due to dislocations and impurities in the Cu2O samples as prepared.

Photovoltaic properties and barrier heights of single‐crystal and polycrystalline Cu2O–Cu contacts

The spectral distribution of the photovoltaic response of polycrystalline and single‐crystal Cu2O–Cu contacts was measured at room temperature using a chopped light technique. The single‐crystal contacts were formed by reducing the (111) surface of single‐crystal Cu2O to copper using atomic hydrogen at room temperature. Prior to the reduction, a departure from stoichiometry was induced in the single crystals by treatment at 750 or 960°C in a known and controllable partial pressure of oxygen. The polycrystalline contacts were prepared from polycrystalline copper plate partially oxidized to Cu2O at 1000°C. The photoresponse measurements indicate that the dominant photovoltaic mechanisms in Cu2O–Cu contacts are hole photoemission from Cu into Cu2O when hv Eg. Barrier heights determined from the threshold of the hole photoemission process measured 0.75±0.06 eV for the single‐crystal contacts and 0.75±0.02 eV for the polycrystalline contacts. It is shown ...

Thermoelectric Effect in Single‐Crystal Cuprous Oxide at High Temperatures

The thermoelectric effect in single‐crystal cuprous oxide, measured at temperatures of 500° to 1130°C and oxygen pressures P of 160 to 2×10—6 Torr, was found always to be positive, indicating that the material is a p‐type semiconductor in these ranges of conditions.Plots of the thermoelectric power Q vs 1/T at different constant oxygen pressures yield parallel straight lines with a slope of 0.75 V. Plots of Q vs logP are mostly straight lines with slopes approximating (—2.3k) / (8q), in which k is Boltzmanns constant and q is the electronic charge.These results can be explained fairly satisfactorily in terms of a modified Wagner model for the defect structure of Cu2O and existing theories of the thermoelectric effect in semiconductors. It is assumed that the concentration of acceptors is a function of both the oxygen pressure and the temperature and that a gradient of acceptors exists along the temperature gradient. Thus, the model shows that the factor 8, originally obtained from conductivity measuremen...

Photovoltaic properties of sputtered n-CdO films on p-Cu2O

The heterojunction CdO/Cu2O was prepared by sputtering CdO films on Cu2O at room temperature. The optical transmission of CdO films at a thickness of ≈1000 A was ≈85%. The analysis of the I–V characteristics at different temperatures gave information of the carrier transport mechanism at the junction. The forward and the reverse dark current is dominated by a tunneling process. Measurements of the open-circuit photovoltage resulted in a curve which indicates a sensitivity range from 2.25 to 2.48 eV, similar to that found in Cu2O MIS solar cells.