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 ...