Fig. 7: Polarization switching and related properties of PEPI.

a Photovoltage dependence of temperature for PEPI. b I–V characteristics with the inversion of polarized direction. Both the direction of Voc and Isc can be reversed by inverting electric poling. c Schematic illustration of switchable photocurrent directions with polarization-related photoexcited carriers with the charge separation under positive polarization direction and negative polarization direction.