Pohl;
Institute;
of;
Solid-State;
Physics,;
Tongji;
University,;
Shanghai;
200092,;
China;
Pohl;
Institute;
of;
Solid-State;
Physics,;
Tongji;
University,;
Shanghai;
200092,;
China;
Pohl;
Institute;
of;
Solid-State;
Physics,;
Tongji;
University,;
Shanghai;
200092,;
China;
poly(ethylene; naphthalene-2,; 6-dicarboxylate),; electret,; charge; stability,; effective; time; constant.;