Characterization of Electronic Transport Properties of Polymer Light-Emitting Diodes (PLEDs) by Impedance Spectroscopy

Abstract

Polymer light-emitting diodes (PLEDs) with four different emissive layers were fabricated. The current efficiencies of the optimized PLEDs with Spiro-Red (SR), Super Orange (SO), Spiro-Green (SG) and Super Yellow (SY), are 1.23, 4.33, 7.70, and 11.2cd/A, respectively. Electron and hole drift mobilities (μ_n, (μ_p), bimolecular recombination constants (β) of the emissive layers in working PLEDs were determined simultaneously using impedance spectroscopy (IS). The bimolecular recombination constants obtained by the IS measurement were found to be two orders of magnitude smaller than the Langevin recombination constants estimated from electron and hole drift mobilities. It is found that there is correlation between the quantum efficiency estimated from the bimolecular recombination constants and the external quantum efficiency of PLEDs.