Construction of Narrowed Deep-Blue Lighting Emitters Based on Fluorenyl Derivatives via Indolocarbazole Fused Modifying Strategy

Abstract

As a classic deep-blue light-emitting fluorophore, fluorene has constructed kinds of star blue emitters featuring tuning optical performances, but their derivatives with narrow-band emission characteristic are still relatively lacking for the requirement of high-resolution display. Here, a feasible strategy is proposed and implemented for improving traditional luminescent building-block, and an indolo[3,2,1-jk]carbazole (ICz) fragment is fused to fluorene framework via one-pot double-halide cyclized coupling (DHCC) reaction. Three fluorene and ICz-based derivatives via fusing-strategy all inherit narrowed emission performance, and show better deep-blue lighting behavior with stable electrical and thermal properties. By inserting large phenyl and spirofluorene, the intermolecular interactions in DPtIDCz and SFtIDCz are tuned significantly and show more saturated deep-blue lighting emission in non-doped OLEDs. Especially, the electroluminescence spectrum of SFtIDCz peaked at 402 nm with narrow full-width at half-maximum (FWHM) of 28 nm, and its CIE coordinate is removed to (0.166, 0.033) from (0.162, 0.051) of tIDCz, implying the importance in adjustment of side chain structure. These results demonstrate that the strategy of using DHCC reaction to achieve fused modification is highly feasible, and the derived materials can maintain commonly the characteristics of both, which have reference significance for the design of more narrow-emission building-blocks in the future.