Triplet–triplet
annihilation (TTA) is an attractive way
to boost the efficiency of conventional fluorescent organic light-emitting
diodes (OLEDs). TTA-active anthracene derivatives are often considered
as state-of-the-art emitters due to the proper energy level alignment.
In this work, TTA properties of a series of highly fluorescent nonsymmetrical
anthracene compounds bearing 9-(4-arylphenyl) moiety and 10-(4-hexylphenyl)
fragments were assessed. Two different methods to enhance the TTA
efficiency are demonstrated. First, the intensity of TTA-based delayed
fluorescence directly depended on the intersystem crossing (ISC) rate.
This ISC rate can be significantly enhanced in more conjugated compounds
due to the resonant alignment of S1 and T2 energy
levels. While enhanced ISC rate slightly quenches the intensity of
prompt fluorescence, the rise of the triplet population boosts the
intensity of resultant delayed fluorescence. Second, the triplet annihilation
rate can be significantly enhanced by optimization of triplet exciton
diffusion regime in the films of anthracene derivatives. We show that
the proper layer preparation technology has a crucial influence on
uniformity and energetic disorder of the film. This enhances the nondispersive
triplet diffusion and increases the resulting delayed fluorescence
intensity.