In a solar cell, when the sunlight impacts the material, a charge is generated. Specifically, this charge corresponds to an electron-hole pair, where an electron is excited to the conduction band, leaving a hole in the valence band. For the cells to be efficient, this pair of charges has to be separated and extracted as efficiently as possible (electron and hole must be directed to opposite electrodes to be captured) to generate an electric current. This is where ferroelectricity comes into play: this property would generate a built-in electric field in the material that could assist charge separation.
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Source: Phys.org