Organic red emitters have shown great prospective applications in full-color displays， fluorescent probes， and photothermal therapy， et al. However， it is still challenging for organic emitters that exhibited intense red emission with a maximum emission （λ_em） above 680 nm in solid state. In this work， two D’-A-D-A-D’ molecules with a benzodithiophene derivative core donor （D）， a benzothiadiazole acceptor （A） and a N-phenyl-2-naphthylamine derivative peripheral electron donor （D'） but differing in fluorine-free D’（RH） and fluorinated D’（RF） were synthesized. Their chemical structures were characterized and confirmed by nuclear magnetic resonance spectroscopy and mass spectroscopy. It is found both of them presented λ_em> 700 nm in solid films. Meanwhile， RF showed a more pronounced aggregation-induced emission enhancement effect and a higher photoluminescence quantum yield than those of RH， attributed to the fluorination induced a larger dipole moment and more twisted structure of RF. LED devices based on RH and RF doped PMMA as colour conversion layers were fabricated， respectively. The maximum brightness of RF based device reaches 2.5-fold of RH based device at a 3.8 V work voltage， and its CIE coordinates （0.70， 0.27） close to standard red light of BT.2020 color gamut. This work provides a promising way for developing organic red emitters with higher brightness and colour-purity.

Organic red emitters;Benzodithiophene;Fluorination;Red light color purity;red LED