Depths of chemical impurity states in Polyethylene; The big picture from first principles

Abstract

Computational quantum mechanics, within the frame work of density functional theory (DFT) was used to determine the depths of impurity states created by common chemical impurities in polyethylene. Depths of traps/hopping sites were between 0.1 eV and 2.4 eV and were classified into shallow traps/hopping sites, deep traps, and deeper traps. Such depths suggest that chemical impurities can play major roles in trapping and hopping processes, can explain the observed activation energy of conduction, and shape the barriers to charge injection. Thus, chemical impurities could dominate high field conduction in polyethylene. The type of impurity bonds and their lengths are correlated with the depth of impurities they create. Such correlation is linear. A procedure to determine depth of states created by an impurity, without using DFT is presented.