Hetero-bichromophore Dyad as a Highly Efficient Triplet Acceptor for Polarity Tuned Triplet-Triplet Annihilation Upconversion.

Triplet-triplet annihilation upconversion (TTA UC) was intensively investigated for developing efficient photosensitizers and emitters. But an emission wavelength tunable TTA UC system with only one emitter was rarely reported. A novel hetero-bichromophore dyad, HB-An, showing solvatochromic emission and high fluorescence quantum yields in weakly polar solvents (such as n-hexane, dichloromethane (DCM), and so on) was used as triplet energy acceptor/emitter for polarity tuned TTA UC. A high TTA UC quantum yield up to 25% was achieved and the UC emission wavelengths can be fine-tuned from cyan to yellow by changing the media polarity. This information will be useful for constructing efficient emitting-light-tunable TTA UC system.