Efficient charge separation at localized 2D ferroelectric domains in perovskite solar cells

Ferroelectric properties can be utilized for efficient charge carrier separation through spontaneous electric polarization. Here, we reveal the potential of ferroelectric-assisted charge separation in 2D perovskites in conjunction with conventional p–n junction photovoltaics. We fabricate high-quality perovskite devices in which a ferroelectric 2D perovskite layer with oppositely polarized regions is locally formed on top of a 3D perovskite layer. Such distinct regions are created near the grain boundary and grain interior regions within the perovskites, and their polarity can be manipulated under bias voltage and light illumination. This configuration promotes distinct potential offsets between the two regions and acts as an excellent electron–hole pair separator. Our findings offer promising opportunities for the design of ferroelectric and p–n junction hybrid photovoltaic devices, resulting in a power conversion efficiency of 26.0%, with an independently certified efficiency of 25.2%.