Characteristics of Electroluminescence in Polyimide Under DC, AC and Square Wave Fields

Photon emission exists in the polymer under electrical stress, that is electroluminescence (EL). It is considered as the dynamic response of charge transport in the material. Among the transport processes, the recombination of charges at the luminescent center is the main issue of EL. However, the characteristics of EL under different excitation electric fields are unclear, especially those under alternating fields, which require further research. In this paper, the EL characteristics of polyimide (PI) under DC, AC and square wave electric fields were measured. And based on the bipolar charge transport (BCT) model, the recombination dynamics process was simulated to further explain the influence of excitation fields on the EL behaviors. The results show that luminescence is more likely to occur under AC and square wave voltages, whose optical signals start to occur at a much lower voltage compared to that under DC. Based on the simulation results, the EL signals are indeed closely related to the charge behavior within insulating materials. The phase dispersion of EL under AC is greater than that under the square wave field. The performance of EL under square waves may be affected by the waveform parameters of voltage, which is worthy of further exploration to understand the EL mechanism under square wave fields.