*Polyimide for Electronic and Electrical Engineering Applications*

injection layer (EIL) and hole injection layer (HIL), respectively. As illustrated in **Figure 2**, the injection of holes from HIL and the injection of electrons from EIL move toward hole transport layer (HTL) and electron transport layer (ETL), respectively.

The charges move from one electrode to the opposite polarity electrode; during the movement, some charges are trapped, some detrapped, and some recombined in the interfacial region due to charges already exist in these regions. The polarity of these interfacial regions depends on the electronic state of the adjacent electrode. In case of PI nanocomposite multilayer structure, the accumulation of charges can depend on the following [10]:


Therefore, the discontinuity of electronic state distribution causes an additive trap at the interface for the transportation of charges.
