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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Steric Modulation of Spiro Structure for Highly Efficient Multiple Resonance Emitters
Yang-Kun Qu1, Dong-Ying Zhou2, Fan-Cheng Kong1
1Institute of Functional Nano & Soft Materials, Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, 199 Ren'ai Road, Suzhou, 215123, Jiangsu, P. R. China.
Abstract:
A multiple resonance thermally activated delayed fluorescence (MR-TADF) molecule with a fused, planar architecture tends to aggregate at high doping ratios, resulting in broad full width at half maximum (FWHM), redshifting electroluminescence peaks, and low device efficiency. Herein, we propose a mono-substituted design strategy by introducing spiro-9,9'-bifluorene (SBF) units with different substituted sites into the MR-TADF system for the first time. As a classic steric group, SBF can hinder interchromophore interactions, leading to high device efficiency (32.2-35.9 %) and narrow-band emission (≈27 nm). Particularly, the shield-like molecule, SF1BN, seldom exhibits a broadened FWHM as the doping ratio rises, which differs from the C3-substituted isomer and unhindered parent emitter. These results manifest an effective method for constructing highly efficient MR-TADF emitters through a spiro strategy and elucidate the feasibility for steric modulation of the spiro structure in π-framework.
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