Dresden 2017 – wissenschaftliches Programm
CPP 21: Organic Electronics and Photovoltaics III: Mobile and Trapped Charges (joint session CPP/DS/HL, organized by CPP)
CPP 21.9: Vortrag
Dienstag, 21. März 2017, 11:45–12:00, ZEU 260
Modelling long-term isothermal charge decay in modified PTFE electrets — •Dmitry Rychkov — University of Potsdam, Potsdam, Germany
Electret stability is usually best characterised by means of charge decay as a function of time. In highly stable electret materials, charge-decay measurements require very lengthy experiments even at elevated temperatures. Isothermal charge-decay curves, however, can be modelled if thermally-stimulated discharge data are known. Here, we attempt to deal with this problem for electrets made from chemically modified polytetrafluoroethylene (PTFE) films. PTFE films were treated with TiCl4 vapor in a flow-type reactor and electrically charged in a positive corona discharge. Using the charge-transport theory by Simmons, frequency factors and energy spectra for the relevant surface traps have been extracted from thermally stimulated surface-potential decay curves. The data were then used to calculate isothermal charge-decay curves at different temperatures. A detailed comparison between the modelled and the experimental curves reveals good agreement at elevated temperatures. At lower temperatures, however, the modelled isothermal charge-decay curves deviate from the experimental ones and show a slower decay, which indicates that additional mechanisms that are not covered in the theory may contribute to the electret-charge decay in this temperature range. We propose a simple phenomenological model to illustrate the effects of such mechanisms and to determine the applicability limits of our charge-decay modelling method.