Strongly enhanced and tunable photovoltaic effect in ferroelectric-paraelectric superlattices

Ever since the first observation of a photovoltaic effect in ferroelectric BaTiO₃, studies have been devoted to analyze this effect, but only a few attempted to engineer an enhancement. In conjunction, the steep progress in thin-film fabrication has opened up a plethora of previously unexplored avenues to tune and enhance material properties via growth in the form of superlattices. In this work, we present a strategy wherein sandwiching a ferroelectric BaTiO₃ in between paraelectric SrTiO₃ and CaTiO₃ in a superlattice form results in a strong and tunable enhancement in photocurrent. Comparison with BaTiO₃ of similar thickness shows the photocurrent in the superlattice is 10³ times higher, despite a nearly two-thirds reduction in the volume of BaTiO₃ The enhancement can be tuned by the periodicity of the superlattice, and persists under 1.5 AM irradiation. Systematic investigations highlight the critical role of large dielectric permittivity and lowered bandgap.