Heterostructure engineering of $CuFeO_2$-based photocathodes through conduction band edge level control of $In_{2-_x}Ga_xO_3$

Abstract

Photoelectrochemical water-splitting is widely studied as a complementary technology of the photovoltaics. Recently, $CuFeO_2$ (CFO) has been attracting attention as a promising photocathode material, due to its earth-abundancy and excellent optoelectronic property. However, its low photo-activity in hydrogen evolution reaction (HER) due to the charge trapping at the surface states is limiting its application. In this work, the manipulation of carrier pathway is attempted by a stepwise over-layer engineering to relieve the charge carrier trapping induced by the surface states, and facilitate the carrier dynamics over CFO based photocathodes. First, Amorphous $Ga_2O_3$ ($a-Ga_2O_3$) was incorporated as an intermediate layer to suppress the surface states and interfacial recombination. Lastly, the band edge alignment of the over-layers was controlled by In alloying on $a-In_2-xGa_xO_3$ as an intermediate layer, resulting in the formation of type II heterostructure with the cascading array of conduction band edge.