History and latest development of ferroelectric-semiconductor coupled photovoltaic devices

Abstract

This paper introduces the history and current research status of the novel ferroelectric-semiconductor coupled photovoltaic devices, in which a ferroelectric field of polarized dipoles from nanoparticles separates the photogenerated carriers. Fabrication of such devices by combining a CdS nanodipole and a CdTe absorber via a feasible method is described, which involves a phase segregation process of CdS from a CdS-CdTe pseudobinary system. An irregular behavior is observed on this type of devices, i.e. the hysteresis of open circuit voltage due to external bias of direct-current (DC) electric field. Other macroscopic and microscopic evidences of the dipole field photovoltaic effect are also described. Meanwhile, similar photovoltaic mechanism observed in other types of solar cells are also discussed, such as organic photovoltaic devices and quantum dot devices with photo-induced dipole polarization field, piezo-phototronic devices, ferroelectric photovoltaic devices, as well as perovskite solar cells. It is apparent that the polarization field of dipoles not only exists in the various types of photovoltaic devices, but also may dominate the behavior of devices. Therefore, we propose that a new concept of dipole field semiconductor devices could be properly used to explain the photovoltaic behavior of both junctional and un-junctional devices. The junctional devices could function with either pn junction or Schottky junction, while the un-junctional devices include all the devices mentioned above. We expect that various innovation should be inspired by this concept in photovoltaic community.