Electrodeposited Cu₂O as Photoelectrodes with Controllable Conductivity Type for Solar Energy Conversion

Electrodeposition of copper acetate under mild acidic conditions followed by a controlled annealing process allowed the manipulation of the oxygen vacancies in the resultant Cu 2 O-based electrodes. The conduction type of the Cu 2 O-based semiconductor was, therefore, tunable, allowing the fabrication of n-type, p-type, and p–n junction photoelectrodes. A transformation of the original n-type conduction to the subsequent p-type nature was observed through the variation of annealing temperature and duration. The observation of anodic and cathodic photocurrents for n-type and p-type thin films confirmed their potential use as photoanodes and photocathodes, respectively, in liquid-junction photoelectrochemical systems. The high carrier densities of the electrodeposited n- and p-type Cu 2 O were estimated to be 8.9 × 10 19 and 1.3 × 10 20 cm –3, respectively, using Mott–Schottky analysis. Furthermore, the p–n junction photoelectrodes in a device configuration also exhibited diode behavior in current–voltage measurements, indicating their potential application in solid-state photovoltaic devices.