Halogenation of terminal of acceptors has been shown to give dramatic improvements in power conversion efficiencies (PCEs) of organic solar cells (OSCs). Similar significant results could be expected from the halogenation of the central units of state-ofthe-art Y-series acceptors. Herein, a pair of acceptors, termed CH6 and CH4, featuring a conjugation-extended phenazine central unit with and without fluorination, have been synthesized. The fluorinated CH6 has enhanced molecular interactions and crystallinity, superior fibrillar network morphology and improved charge generation and transport in blend films, thus affording a higher PCE of 18.33 % for CH6-based binary OSCs compared to 16.49 % for the non-fluorinated CH4. The new central site offers further opportunities for structural optimization of Y-series molecules to afford better-performed OSCs and reveals the effectiveness of fluorination on central units.

Halogenation of terminal of acceptors has been shown to give dramatic improvements in power conversion efficiencies (PCEs) of organic solar cells (OSCs). Similar significant results could be expected from the halogenation of the central units of state-ofthe-art Y-series acceptors. Herein, a pair of acceptors, termed CH6 and CH4, featuring a conjugation-extended phenazine central unit with and without fluorination, have been synthesized. The fluorinated CH6 has enhanced molecular interactions and crystallinity, superior fibrillar network morphology and improved charge generation and transport in blend films, thus affording a higher PCE of 18.33 % for CH6-based binary OSCs compared to 16.49 % for the non-fluorinated CH4. The new central site offers further opportunities for structural optimization of Y-series molecules to afford better-performed OSCs and reveals the effectiveness of fluorination on central units.

A conjugated polymer-based fluorescence sensor, namely, PTNPy, was constructed on the basis of a polythiophene scaffold coupled with dimethylpyridylamine (DPA) groups in side chains for the consecutive detection and quantification of Cu 2+ and Hcy in a perfect aqueous medium. A dramatic fluorescence quenching of PTNPy by the addition of Cu 2+ was observed in Tris–HCl buffer solution (2 mM, pH 7.4), demonstrating a quick (<1 min) and highly selective response to Cu 2+ with a low limit of detection of 6.79 nM. Subsequently, the Cu 2+ -quenched fluorescence of PTNPy can be completely recovered by homocysteine (Hcy), showing excellent selectivity to Hcy over other competitive species such as cysteine and glutathione. Thanks to the low cytotoxicity and lysosomal targeting ability of PTNPy, it was further applied as an optical sensor for the sequential imaging of Cu 2+ and Hcy in HeLa cells. More importantly, Hcy concentration was linearly related to the fluorescence intensity of PTNPy in living cells, demonstrating huge potential for real-time monitoring the fluctuation of Hcy levels in living cells.