The electrical excitation of a compound leads to a significant amount (75%) of triplet excited molecules which, in case of pure singlet emitters, relax via non-radiative pathways and therefore do not contribute to the overall light emission (cf. Figure 1A). This fundamentally limits the efficiency of organic light-emitting diodes (OLEDs). Compounds with a small energy difference between their singlet and triplet excited states can circumvent this unfavorable energy loss by displaying thermally activated delayed fluorescence (TADF) which allows reverse intersystem crossing and thus repopulation of the emissive singlet state S1 (cf. Figure 1B). Adachi et al. have shown that donor-spiro-acceptor compounds fulfill this prerequisite and can indeed be utilized as efficient TADF emitters. To improve the versatility of this architecture, we set out to synthesize donor-spiro-acceptor compounds based on electron-deficient tricoordinate boron centers as acceptor units. The electron withdrawing behavior of boryl groups is strongly influenced by the substituents attached to the boron atom and can therefore be fine-tuned over a wide range. Thus, the acceptor moiety acts as a setscrew to control the optoelectronic properties of the TADF materials. The synthesis and photophysical characterization of such compounds will be discussed in this presentation.

Boron-based donor-spiro-acceptor compounds as TADF emitters

253rd National Meeting (2017)

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