Polarity-enhanced cationic π-conjugation in Mn( <scp>ii</scp> )-based metal halide luminescent materials: boosting quantum yield and enabling anti-counterfeiting

Low-dimensional lead-free Mn( ii )-based organic–inorganic metal halides are promising luminescent materials, yet molecular-level fine-tuning of organic structures to achieve high quantum yield and functional red-light emission remains challenging.