Fig. 2: Bulk photovoltaic (BPV) currents in multi-domain BaTiO₃.

a Simulation setup to emulate the experimental BPV measurement. The light polarization E_ph, local ferroelectric polarization P, and BPV tensor β are defined with respect to the xyz axes. Voltage (V₀) is applied on the bottom electrode while the top electrode is grounded. The lower panel illustrates an alternating a⁺/c⁺ domain with a number of domain walls (N_DWs) of 2, a domain wall spacing (d_DWs) of 30 nm, and a simulation size of 60 nm. The simulation geometry was rotated 45 degrees along the x-axis for easy representation. The size of the domain wall is ~1 nm. b The short-circuit current density (J_SC) as a function of light polarization angle (θ_ph) with fixed light intensity I_ph = 5.6 W/cm², BPV tensor component β₃₁ = − 93 nA/W, β₃₃ = − 55 nA/W for different N_DWs (2–16) and at a fixed simulation size of 60 nm. Results for a single a⁺ domain, a single c⁺ domain, and their average (black dashed line) are also included for comparison. c Schematics of a continuous transition of polarization along the [011] direction across the 90-degree domain wall separating a⁺ and c⁺ domains. d Simulated J_SC as a function of light polarization angle (θ_ph) with fixed light intensity I_ph = 5.6 W/cm² for an alternating a⁺/c⁺ domain, with a volume ratio of domain walls to bulk domains equals to 1:300. Green curve corresponds to the case of a constant BPV tensor (β_ijk) with values of β₃₁ = − 93 nA/W and β₃₃ = − 55 nA/W, while the red curve corresponds to the case where the BPV tensor is modified at the domain walls with the values of β₃₁ = + 7300 nA/W and β₃₃ = + 13870 nA/W. The reference experimental data (blue dots) are sourced from Noguchi, Y. et al., J. Appl. Phys. 129, 084101 (2021).