The investigation of the diffusion length of cathode materials in organic light emitting devices through impedance characteristics

摘要

A non-destructive method to measure the diffusion length of the cathode materials into the organic layers in organic light emitting diodes (OLEDs) is demonstrated. The measurement is based on a correlation between the transition voltage in the impedance-voltage (Z-V) characteristics, the density of the accumulation charges, and the thickness of the electron transport layers (ETLs). The transition voltages in Z-V characteristics deviate from the theoretical values owing to the decrease of the effective ETL thickness caused by the diffusion of the cathode materials, which can be used to measure the diffusion length of metal ions into organic layers in OLEDs.