Anomalous Photovoltaic Effect in Centrosymmetric Ferroelastic BiVO₄

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• The anomalous photovoltaic (APV) effect is rarely observed in materials with inversion symmetry.
• Understanding the mechanisms behind APV effects in centrosymmetric materials is crucial for novel device applications.

Purpose of the Study:

• To report the discovery of the APV effect in centrosymmetric bismuth vanadate (BiVO4).
• To investigate the relationship between stress modulation and photovoltage.
• To elucidate the underlying mechanism of the observed APV effect.

Main Methods:

• Experimental observation of photovoltage and photocurrent in BiVO4 ceramics and single crystals under visible light.
• Stress modulation experiments to analyze photovoltage reversal and directional dependence.
• Microstructure and strain-field analysis to identify localized asymmetries.

Main Results:

• Significant above-bandgap photovoltage and steady-state photocurrent were observed in BiVO4.
• Photovoltaic voltage reversal and a sine-function relationship with stress angle were demonstrated.
• Localized asymmetries due to strain fluctuations were identified in the bulk material.

Conclusions:

• The APV effect in centrosymmetric BiVO4 is attributed to flexoelectric coupling via a strain-induced local polarization mechanism.
• This discovery enables new applications for BiVO4 in optoelectronics.
• The study provides deeper insights into the mechanisms of the APV effect in centrosymmetric materials.