Through‐Space vs Through‐Bond Charge Transfer Fluorophores as Emitters for Efficient Blue Electroluminescent Devices

Abstract Herein, we report the design, synthesis, and properties of two donor‐π‐acceptor (D‐π‐A) charge transfer fluorophores pursuing an efficient deep blue emitter for organic light‐emitting diode (OLED). TCyCN and TPhCN comprise triphenylamine as a donor and benzonitrile as an acceptor connecting by either [2.2]paracyclophane (Cy) as a through‐space π‐linker or phenyl ring (Ph) as a through‐bond π‐linker, respectively. In thin film, TCyCN shows deep blue emission with moderate fluorescence efficiency, while TPhCN displays cyan blue emission with a high fluorescence efficiency. The two molecules feature hybridized local and charge‐transfer states with good thermal stability and balanced charge transport properties. They are successfully employed as non‐doped blue emissive layers in OLEDs. The TCyCN‐based device emits deep blue light peaked at 425 nm (CIE coordinates of (0.157, 0.076)) with a moderate electroluminescent (EL) performance (EQE_max=3.23 % and CE_max=2.06 cd A⁻¹), while the TPhCN‐based device attains an excellent EL performance (EQE_max=6.24 % and CE_max=8.26 cd A⁻¹) with cyan blue emission peaked at 490 nm. This work provides insight into the relationship between molecular design and properties of D‐π‐A emitters, offering a guideline for tailoring new organic compounds for organic optoelectronics.