Surface modification and stoichiometry control of Cu2O/SnO2 heterojunction solar cell by an ultrathin MgO tunneling layer

Abstract Here, we demonstrated the potential of an ultrathin Mg-rich MgO tunneling layer as a passivation layer for earth-abundant Cu 2 O based solar cell. An ultrathin Mg-rich MgO layer was introduced to the interface of Cu 2 O/SnO 2 heterojunction by electron beam evaporation, which greatly enhanced the efficiency of Cu 2 O/SnO 2 heterojunction solar cell. The MgO layer was found to significantly reduce the CuO defect density and create a stoichiometry Cu 2 O surface confirmed by high-resolution X-ray photoelectron spectroscopy. Thus, charge recombination caused by interface defect was mitigated bringing an increased device efficiency. This work highlights the need for stoichiometric Cu 2 O surface in Cu 2 O-based solar cells.