Defect engineering of charge transport and photovoltaic effect in BiFeO3 films

Bismuth ferrite (BiFeO₃) is an attractive multiferroic material, extensively explored in photoferroelectric investigations. However, its applications are hindered by the high leakage current, requiring precise control of charge transport properties. Defect engineering has emerged as a promising strategy to address this issue: controlling the defect chemistry, particularly oxygen vacancies, is key to tuning the electrical properties. This study investigates the influence of 5%

- and 2%

-doping on the dark and light-induced charge transport properties of polycrystalline BiFeO₃ films. Our results demonstrate that

reduces dark conductivity by decreasing oxygen vacancy concentration with no change in the physical nature of the charge transport mechanism. In contrast,

modifies the charge transport mechanism, increasing low-field (E $<$ 100 kVcm^-1) dark conductivity while drastically reducing high-field (E $>$ 250 kVcm^-1) dark conductivity. This tuning of the defect chemistry is also key to enhance the photovoltages of the bulk photovoltaic effect in BiFeO₃. High photoinduced electric fields up to 7 kVcm^-1 and low photoconductivity values are obtained with

-doping, while high short-circuit photocurrent values are obtained with

-doping.