Numerical analysis of space charge electric field and its effect on TSDC measurement in thin polymer films

The internal electric field and potential in thin polymer film caused by injected charges were numerically analyzed and some paradoxical TSDC experimental results and the effect of internal electric field on the trap parameters obtained from TSDC measurement were discussed. It´s found that, under short-circuit of the external electrodes, one zero electrical field plane and one potential peak appeared within the film and their positions depended on the spatial distribution of the space charges. The internal electric filed can vary from -3 times 10⁷V/m to 5 times 10⁷V/m in the case of a space charge density 100 C/m³ at the interface between cathode and polymer film. The large internal electric field has an important impact on the space charge transportation due to Poole-Frenkel effect, which can change the trap depth. In addition, the reversed current peak in TSDC spectrum, the reduced space charge quantity that can be measured by TSDC may all be resulted from the internal electric field and potential distribution.