Abstract
The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. Ferroelectrics have received renewed attention because of the ability to deliver a high voltage in the presence of ferroelastic domain walls (DWs). In recent years, there has been considerable debate over the impact of the DWs on the PV effects, owing to lack of information on the bulk PV tensor of host ferroelectrics. In this article, we provide the first direct evidence of an unusually large PV response induced by ferroelastic DWs—termed ‘DW’-PV effect. The precise estimation of the bulk PV tensor in single crystals of barium titanate enables us to quantify the giant PV effect driven by 90° DWs. We show that the DW-PV effect arises from an effective electric field consisting of a potential step and a local PV component in the 90° DW region. This work offers a starting point for further investigation into the DW-PV effect of alternative systems and opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structures in either bulk or thin-film form.
Highlights
The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells
The bulk PV effect has been extensively studied in ferroelectric oxides[1,2,3,4,5,6,7,8], compound semiconductors[9,10] and fluoride polymers[11]
Recent studies on ferroelectric thin films have demonstrated that bismuth ferrite (BiFeO3: BFO) with ferroelastic domain walls (DWs) delivers above-bandgap voltages that can be tuned by the number of the DWs13
Summary
The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. The temperature-dependent PV studies have revealed that BFO films generate a high photovoltage by controlling the conductivity of the DWs15 This anomalous PV effect is thought to be due to the bulk PV effect, not to the electrostatic potential step at the DWs. Essentially, the bulk PV effect arises from spatial symmetry breaking in polar materials[16,17] and can be described in terms of the bulk PV tensor[18]. The precise estimation of the bulk PV tensor allows us to quantify the contribution of 90° DWs in BT single crystals, revealing that the field strength due to the DW-PV effect is far beyond the bulk PV effect We show that this extremely large field stems from an effective electric field consisting of a potential step and a local PV component in the 90° DW region
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