Fabrication of Cu2O/Fe–O heterojunction solar cells by electrodeposition

• FeOOH thin films were deposited by electrodeposition.
• FeOOH was transformed to Fe2O3 by annealing in air.
• Cu2O was electrodeposited on both as-deposited and annealed Fe–O films.
• Both the Cu2O/FeOOH and Cu2O/Fe2O3 heterostructures act as a solar cell.

Cu2O/Fe–O heterojunction solar cells were successfully fabricated by electrodeposition method. The as-deposited thin film exhibited signature Raman peaks associated to γ-FeOOH. By thermal annealing in air at 100–400 °C, different Fe2O3 polymorphs were produced. Both as-deposited and annealed Fe–O films showed n-type conductivity with approximated band gap of 2.1–2.3 eV. Resistivity was ~ 680 Ω cm for γ-FeOOH and > 700 Ω cm for Fe2O3 films. Cu2O as the p-type layer was partnered with as-deposited and annealed Fe–O thin films to fabricate different heterojunctions based on Fe oxides compounds. Remarkably, all the fabricated Cu2O/Fe–O heterostructures exhibited photovoltaic characteristics (open circuit voltage, VOC = 38–108 mV and short circuit current density, JSC = 0.74–1.58 mA/cm2), although no appreciable differences were found on their solar cell parameters. The present results strongly suggest the potential of Fe–O based semiconductors for solar cell fabrication.