Lighting up aggregate emission of perylene diimide by leveraging polymerization-mediated through-space charge transfer and π-π stacking

The molecular engineering of fluorescent organic/polymeric materials, specifically those emitting in the deep red to near-infrared spectrum, is vital for advancements in optoelectronics and biomedicine. Perylene diimide (PDI), a well-known fluorescent scaffold, offers high thermal and photophysical stability but suffers from fluorescence quenching in solid or aggregate states due to intense π-π interactions. To mitigate this, simple and versatile methods for strong PDI aggregate emission without extensive synthetic demands are highly desirable but still lacking. Here, we report a straightforward strategy to enhance the solid-state emission of PDI by introducing certain degree of through-space charge transfer (TSCT) via controlled radical polymerization, which can efficiently distort the typical face-to-face PDI stacking, enabling greatly enhanced deep red emission. This is achieved by growing electron-donating star-shape styrenic (co)polymers from a multidirectional electron-accepting PDI initiator. The incorporation of polycyclic aromatic monomers further shifted the emission into the near-infrared region, albeit with a reduced intensity. Overall, the emission of the PDI-based TSCT polymers can be systematically manipulated by leveraging the balance between PDI stacking and the TSCT degree, as confirmed by both experimental study and theoretical calculations. Our approach circumvents complex synthetic procedures, offering highly emissive materials with large Stokes shifts and showing broad potential for optoelectronic technology.