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A charging method for electrets is proposed, based on interfacial polarization in double-layer media. It can achieve a high density and excellent stability of the charge storage as well as good uniformity of the surface potential distribution on electret materials. An equation for the charge accumulation at the interface of double-layer dielectrics is derived. FEP film electrets are successfully obtained by means of this charging method with an auxiliary PP-layer. The effect of the charging voltage on the storage performance shows that the surface potential of FEP films increases linearly with the charging voltage. This is in good agreement with the theoretical analysis. The effect of the charging temperature is ascribed to the change in conductivity of the two dielectrics, whereby the current density in particular across the PP layer increases with a rise in charging temperature. In addition, the charge is captured by deeper traps, while the deposition charge density increases. [ABSTRACT FROM AUTHOR]