Cross linkable phosphorescent polymer-LEDs based on a soluble new iridium complex ((Btp)₂Ir(III)(acac)-Ox)

PVK is a prototypical host for polymer based phosphorescent OLEDs. We report the photo (PL) and electroluminescence (EL) properties of phosphorescent organic light emitting diodes (OLEDs) based on poly(vinylcarbazole) (PVK) derivatives doped with cyclometalated Ir(III) complexes. To allow for stable morphology as well as photopatternability, both the host and guest materials were rendered cross-linkable by attaching a cross linking oxetane moiety. Regarding the PVK matrix we also used a new derivative (PVK-Cin) of poly(vinylcarbazole) (PVK) that was prepared by tethering cinnamate pendants to the carbazole group through an octylene spacer. While the use of the oxcetane moieties attached to the ligands of the Ir complex slightly improves the luminescence efficiency, the use of oxcetane derivatized PVK and the associated catalyst result in poor performance. In contrast, the use of the (catalyst free) cinnamate derivatized PVK results in high efficiency cross-linked PLEDs with efficiency higher than 4.5 cd/A. Photopatternability of the new PVK based-polymer was investigated through photocrosslinking reaction under UV light illumination (= 254 nm). The blends of PVK-Cin and a soluble (Btp) ₂Ir(III)(acac)Ox were employed for studying a photocrosslinking behavior. We observed that PVK-Cin readily undergoes 2π + 2π cycloaddition when exposed to the UV light (λ_max = 254 nm) at 110 °C without photoinitiator.