Band-Gap Reduction in (Bi Cr O3)m/(Bi Fe O3)n Superlattices: Designing Low-Band-Gap Ferroelectrics
Abstract
Ferroelectric Bi Fe O3 is promising for photovoltaic applications, especially in regard to the exploitation of ferroelectric photovoltaic effects for charge separation. However, its large band gap limits efficient sunlight absorption. Here, we demonstrate a new strategy to effectively tune the band gap of tetragonal Bi Fe O3 via superlattice structuring with the ferroelectric Bi Cr O3. The (Bi Cr O3)m/(Bi Fe O3)n superlattices are found to exhibit conventional ferroelectric properties, but low fundamental band gaps, smaller than either of the parent materials. First-principles calculations reveal that the unexpected band-gap reduction is induced by charge reconstruction due to lattice strain, octahedral distortion, and polarization discontinuity at the Bi Cr O3-Bi Fe O3 interfaces. Ultimately, these results provide a new strategy, in the form of superlattice structuring, which could open the door to the creation of efficient ferroelectric photovoltaics.
- Publication:
-
Physical Review Applied
- Pub Date:
- October 2018
- DOI:
- 10.1103/PhysRevApplied.10.044004
- Bibcode:
- 2018PhRvP..10d4004Z