Interface band structure engineering by ferroelectric polarization in perovskite solar cells

• Switchable ferroelectric domains in CH3NH3PbI3 have been revealed.
• Negative poling deteriorates and positive poling assists PV performance.
• Switching of CH3NH3PbI3 polarization lead to J–V hysteretic behavior.
• Poling and J–V direction impact PV performance for ferroelectric oxide solar cells.

We demonstrate the presence of ferroelectric domains in CH3NH3PbI3 by piezoresponse force microscopy and quantify the coercive field to the switching of the polarization of ferroelectric CH3NH3PbI3. For CH3NH3PbI3 perovskite solar cell, negative electric poling decreases the net built-in electric field, driving potential and width of depletion region inside the absorber layer, which hinders charge separation and deteriorates photovoltaic performance; while positive poling boosts these electrostatic parameters and therefore improves the charge separation inside the absorber. Low coercive field (8 kV/cm) enables the switching of CH3NH3PbI3 polarization during the current density–voltage (J–V) measurement. Forward scan initially activates the negative poling, whereas reverse scan first activates the positive poling, which can lead to the J–V hysteretic behavior. Comparative analysis with a traditional ferroelectric 0.25BaTiO3–0.75BiFeO3 solar cell is conducted to confirm the impact of ferroelectric polarization and J–V scanning direction on photovoltaic performance.

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