The energy distribution of traps in polymers based on isothermal surface potential decay measurement

Charge traps have great influence on charge transport, trapping and recombination in solid dielectrics such as polymers. In this paper, the energy distribution of traps in three polymers i.e. low density polyethylene (LDPE), polypropylene (PP) and polyester (PET) has been studied, based on the isothermal surface potential decay measurement. Trap measurement and calculation formula is deduced and a trap non-contact measurement setup is specially designed. One excellence of the device is that electron or hole trap parameters can be determined by choosing negative or positive charging, respectively. On the basis of the formula acquired, the electron and hole trapping parameters of the material can be evaluated. Results reveal that potential of PET decays the fastest among these materials, probably because there is more charge injection into the bulk during corona charging. With the enhancement of temperature, both negative and positive potentials decay faster. The trap density of PET is much higher than LDPE and PP, which reveals the high polarity of the PET molecule.