Piezoelectricity of polymer electrets with space charge

New polymer piezoelectric materials have been the focus for electrets study since the concept of space charge electret piezoelectricity was proposed in 1970s.Its piezoelectric mechanism is very different from that of ferroelectric polymer materials such as PVDF,whose piezoelectricity is due to the charges asymmetrically moving to the electrode.In this paper the research progress on space charge electret piezoelectric polymer materials with closed or open-porous structure and soft/hard hybrid structure was reviewed and the development prospects were also discussed.