Estimation of charge injection at Al/LDPE interface based on space charge and external current measurement.

This article focuses on a quantitative method to estimate charge injection at the metal/polymer interface, specifically at the aluminum/low density polyethylene (Al/LDPE) interface, by simultaneously measuring space charge and current under quasi-unipolar conditions. Using a double-layer sample with a blocking layer to eliminate extraction current and accounting for displacement current, the study finds that the square root of the electrode electric field and the logarithm of the injection current exhibit a linear relationship consistent with the Poole–Frenkel effect rather than the commonly applied Schottky effect. The coefficients β for negative and positive charge injection at the Al/LDPE interface are approximately 8.44 × 10⁻²⁴ and 8.32 × 10⁻²⁴, respectively, with corresponding injection barriers of about 1.23 and 1.24 eV. This method provides a more accurate analysis of charge injection dynamics at metal/polymer interfaces, which is critical for understanding electrical aging in polymer insulation under DC conditions.