Organic light emitting diodes (OLEDs) displaying a wide range of emission colors with emission peaks from 450 to 665 nm using a single emitting material, avobenzone boron difluoride (AVB-BF 2 ), are This article is protected by copyright. All rights reserved. 2 reported. Color tuning is achieved by controlling the aggregation of AVB-BF 2 and the formation of a "triadic" exciplex of an AVB-BF 2 dimer and a host molecule. Various electroluminescent devices containing AVB-BF 2 cover the whole visible light spectrum and a white-emitting device with CIE coordinates of (0.35, 0.37) is obtained with a single emitting material in a single emissive layer.Furthermore, an exceptionally high external quantum efficiency of nearly 13% is achieved for a greenemitting OLED because AVB-BF 2 exhibits thermally activated delayed fluorescence by forming the exciplex.

We have investigated concentration-dependent fluorescence color tuning of BF 2 AVB in a poly(methyl methacrylate) film. BF 2 AVB exhibits a color change from purple-blue to orange via green, and then crystals segregate from the polymer matrix. We analyzed the fluorescence and fluorescence excitation spectral change as a function of the BF 2 AVB concentration in the film. We also obtained fluorescence microscope images to confirm the miscibility and crystallization properties in the films. This originates from the aggregated state formed in the polymer matrix depending on the stacking structure of the parallel (B-phase), antiparallel (G-phase), and amorphous states. The emissive species change with increasing BF 2 AVB concentration. The polymer matrix isolation method enables not only directly visualization of the dynamics of the crystal formation process and Ostwald's rule of stages by fluorescence changes, but it also enables device fabrication, such as fabrication of organic light-emitting diodes and luminescent solar concentrators.

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