Effect of trapped electrons on the transient current density and luminance of organic light-emitting diode.

Transient current density and luminance from an organic light-emitting diode (OLED) driven by voltage pulses were investigated. Waveforms with different repetition rate, duty cycle, off-period, and on-period were used to study the injection and transport characteristics of electron and holes in an OLED under pulse operation. It was found that trapped electrons inside the emitting layer (EML) and the electron transporting layer (ETL) material, tris(8-hydroxyquinolate)aluminum (Alq₃) helped for attracting the holes into the EML/ETL and reducing the driving voltage, which was further confirmed from the analysis of capacitance–voltage and displacement current measurement. The relaxation time and trapped filling time of the trapped electrons in Alq₃ layer were ~200 µs and ~600 µs with 6 V pulse operation, respectively. [ABSTRACT FROM AUTHOR]