Influence of the applied charge on the electro-chemical degradation in green phosphorescent organic light emitting diodes

• Influence of the applied charge on the chemical degradation processes of green OLEDs.
• Electro-chemical degradation is investigated by LDI-TOF-MS technique.
• BPhen polymeric species and the Ir(ppy)3-based reaction products are detected.
• [Ir(ppy)2BPhen]+ formation depends strongly on the amount of the applied charge.
• BPhen products formation show a much different behaviour.

The influence of the current density on the chemical degradation processes of a phosphorescent OLED based on Ir(ppy)3 emitter is investigated by laser-desorption/ionization time-of-flight mass spectrometry. Comparing the mass spectra collected for unaged and aged OLEDs, the formation of different chemical degradation products could be detected and are identified as dimer and trimer products of BPhen as well as Cs-adducts of these polymers and the well-known emitter-BPhen-adduct ([Ir(ppy)2BPhen]+). In this work, we will show that the formation of [Ir(ppy)2BPhen]+ depends strongly on the amount of the charge flowing through the device, where the other degradation products show a much different behaviour.

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