Dependence of interfacial properties of p-Cu2O/electrolyte and p-Cu2O/Au junctions on the electrodeposition bath pH of p-Cu2O films

Improvements in electrodeposited cuprous oxide (Cu2O) junction devices could contribute to development of a wider range of affordable and environmentally friendly electronic devices. In this regard, ability of controlling interfacial properties of contacts of Cu2O thin films with other suitable materials will be a very important property. A study on interfacial properties of p-Cu2O/Au and p-Cu2O/electrolyte junctions was conducted using capacitance-voltage and current-voltage measurements. It was found that pH of National Taiwan p-Cu2O film deposition bath has a significant effect on junction properties of Cu2O. Particularly, flat band potential at p-Cu2O/electrolyte interface and built-in potential at p-Cu2O/Au interface were shifted positively by the increase of deposition bath pH of p-Cu2O films. Also, it was revealed that the shift was more pronounce at p-Cu2O/Au interface compared to that at p-Cu2O/electrolyte interface. The observed shifts in flat band potential and built in potentials were correlated with the shifts in relative band edge positions at the interfaces and with the change in net surface charge on the interfacial layers. It was observed, for the first time, that built in potential at p-Cu2O/Au junction can be controlled with bath pH of p-Cu2O films so that the junction can make either ohmic or non ohmic. Further, it was found that surface modification of p-Cu2O films with sulphidation reduces barrier height at p-Cu2O/Au junction and make the contact ohmic irrespective of bath pH of p-Cu2O films. We report here, for the first time, that relative band edge position at interfaces of electrodeposited p-Cu2O junctions can be controlled with pH of film deposition bath and surface modification. This will be very useful in application of electrodeposited p-Cu2O thin films in solar cells and other junction devices.