Electronic Properties of Polyethylene Naphthalate as Derived from Photo-Stimulated Discharge and Photoluminescence Experiments

The electronic properties of thin films of poly(ethylene 2,6-naphthalate) -PEN, are investigated based on their photo-physical (optical absorption, photoluminescence) and electrical (space charge distribution, photo-stimulated discharge) behavior. Photo-stimulated currents are associated with optical absorption of the material leading to space charge dissipation as demonstrated by space charge distribution measurement. Based on this set of experimental results and on recently published calculations on molecular dynamics, we propose a new scheme for the electronic levels of PEN. This scheme allows understanding the mechanisms at play in photo-stimulated discharge. One of the main conclusion of our work is that photo-stimulated current measurements do not probe the energy level of traps. The detrapping of charges results from a two-step process where the photon energy is absorbed by chromophores that restitute a part of this energy to trapped charges through various mechanisms.