High-efficiency bulk photovoltaic effect with ferroelectric-increased shift current

Area of Science:

• Materials Science
• Solid State Physics
• Renewable Energy

Background:

• Bulk photovoltaic (BPV) effect, driven by shift currents in symmetry-breaking materials, offers a route beyond the Shockley-Queisser limit for solar cells.
• Current BPV devices face limitations in open-circuit voltage (V_oc) and short-circuit current density (J_sc), hindering photoelectric conversion efficiency.

Purpose of the Study:

• To identify BPV materials for co-optimizing V_oc and J_sc.
• To enhance BPV efficiency through ferroelectric engineered shift currents.
• To demonstrate a high-efficiency BPV device using NbOBr₂.

Main Methods:

• Theoretical analysis and experimental validation.
• Fabrication of a two-dimensional in-plane device using ferroelectric NbOBr₂.
• Investigation of BPV effect dominated by giant shift current.

Main Results:

• NbOBr₂ devices exhibited a record-high J_sc in their spontaneous polarization state.
• Electrically aligned polarization in NbOBr₂ led to simultaneous enhancement of V_oc and J_sc.
• Achieved a colossal photoelectric conversion efficiency of 1.25%, a four-order-of-magnitude improvement.

Conclusions:

• Ferroelectric engineered shift currents offer a promising strategy for high-efficiency BPV solar cells.
• NbOBr₂ is a viable material for next-generation BPV devices.
• The findings provide a pathway for screening and developing superior BPV materials.