Behavior of charge carriers and excitons in multilayer organic light-emitting diodes made from a polysilane polymer as monitored with electroluminescence

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Abstract
Using electroluminescence (EL) as a monitor, we have investigated the behavior of charge carriers injected from electrodes and excitons generated by the recombination of charge carriers in multilayer organic light‐emitting diodes (LEDs) using poly(methylphenylsilane) (PMPS) as a hole transporting material. Our multilayer LEDs have two or three functional organic layers including Coumarin 6 [3‐(2′‐benzothiazolyl)‐7‐diethylaminocoumarin, abbreviated as C6] and/or tris‐(8‐hydroxyquinoline) aluminum layers as well as a PMPS layer. When the LEDs were fabricated, two parameters of the C6 layer were changed, the layer thickness (30–120 nm) and the dye concentration (1–100 wt %). We employed a combined analysis of the dependence of the EL spectra on the thickness and dye concentration of the C6 layer, the dye‐selective fluorescence spectra and the current–voltage–EL characteristics, to reveal the thickness of the electron–hole capture zone and the behavior of charge carriers and excitons during operation in these LEDs.