Borondipyrromethene (Bodipy) dyes with strong solid-state photoluminescence are highly desirable for their applications in OLEDs. In this work, a series of meso-(4-R-C6H4)-substituted Bodipy dyes (R = H for B1; R = (OCH2CH2)nOCH2CH3, n = 0-3 for B2-B5, respectively) were prepared through an acid-catalyzed reaction. The flexible ether groups attached to the periphery of B2-B5 are expected to influence the molecular arrangement and intermolecular interactions in solid state. Crystallographic analysis of B1-B4 reveals that the meso-phenyl ring is almost orthogonal to the indacene plane. Intermolecular pi-pi interactions are observed in B1 but absent in B2-B4. As a consequence, the dye B1 is weakly emissive in solid state, while B2-B4 emit strongly in the red region with emission quantum yields of up to 0.33. The PMMA films doped with B2 show two separated emission peaks; their relative intensity is concentration dependent, leading to the fluorescence color varying from greenish yellow to red as the concentrations successively increased from 5 to 80 wt%. The formation of dimers in the ground state is found to be responsible for the red emission in the condensed state. Efficient OLEDs were fabricated by doping 2 wt% B2-B4 as emitters and gave high luminance, current efficiency, and external quantum efficiency of up to 920 cd m-2, 8.00 cd A-1, and 2.15%, respectively.

Journal of Materials Chemistry C, 2014