Green Grinding-Coassembly Engineering toward Intrinsically Luminescent Tetracene in Cocrystals

Developing
an effective and green method toward organic functional
cocrystals based on the solubility-mismatched coformers is highly
desirable and very important. Herein, we applied a green two-step
liquid-assisted-grinding coassembly (LAGC) in fabricating tetracene-octafluoronaphthalene
(TC-OFN) cocrystals from solubility-mismatched pairs of tetracene
(TC, poorly soluble, 0.2 mg mL–1) and octafluoronaphthalene
(OFN, highly soluble, 0.2 × 104 mg mL–1). Such cocrystals are extremely difficult to prepare through the
common solution-processing strategies. More importantly, this two-step
LAGC process could allow us to efficiently prepare TC-OFN cocrystals
in gram scale. The as-prepared cocrystals displayed the intrinsic
green emission of TC with much higher photoluminescence quantum yield
(13.75%) comparing with the pure solid TC with the almost-quenched
emission (0.41%, aggregation-caused quenching (ACQ)). The ultrafast
spectra study on these cocrystals verifies the successful barrier
function of OFN molecules in interrupting the well-known singlet fission
(SF) in TC solids. Furthermore, this method can allow us to easily
fabricate fluorescent TC-OFN water inks, which can be employed to
prepare luminescent paintings or highly emissive ultratransparent/flexible
films.