Fluorescent organic/polymeric materials with deep red to near-infrared emission color are drawing widespread attention due to their great potential for optoelectronic devices, notably organic light-emitting diodes (OLEDs), and for biomedical applications such as in vivo fluorescence imaging. As one of the most commonly used scaffolds for synthesizing such functional materials, perylene-3,4,9,10-tetracarboxylic acid diimide (PDI) exhibits strong fluorescence and good thermal and photophysical stability. As the most important feature, the primary PDI fluorophore possesses intense yellow-green photoluminescence with near-unity quantum yield in diluted solutions. However, in solid or aggregate states, its fluorescence turns red and gets dramatically quenched, owing to the strong π-π stacking induced dipole-dipole interactions. Here, we present a simple approach to remarkably enhance the aggregate-state emission of PDI via controlled polymerization-mediated charge transfer. Using an imide-functionalized PDI as the initiator, well-defined four-arm (co)polymers with simple structures (Figure ) were synthesized by atom transfer radical polymerization (ATRP). The PDI polymers showed a PLQY of up to 45% in solid films and a single-peak emission wavelength at 625-655 nm. A further increase of the polymer PLQY to 62% was simply achieved by blending with a polystyrene matrix, preserving the singlepeak aggregate emission, albeit with a slight blueshift. In addition, a series of polycyclic aromatic monomers were introduced as stronger electron donors via copolymerization with styrene. The resulting copolymers showed gradually redshifted emission to the near-infrared (NIR) region with the increase of the co-monomer's electron density, accompanied by a significant decrease of the PLQY in solid state (Figure ). Molecular dynamics (MD) simulations were conducted to illustrate the impact of polymer structure on the PDI stacking configurations. Time-dependent density functional theory (TD-DFT)-based calculations were performed to elucidate the ground-state and singlet excited-state energies generated by the donor-to-acceptor (D-A) TSCT processes. Both experimental and theoretical investigations suggest that polymerization-mediated TSCT can promote strong aggregate emission of PDI in solid state via distorting the typical molecular face-to-face stacking of the PDI scaffold. We further demonstrate that the PDI polymers can be used as highly emissive coatings in fabrication of fluorescent 3D waveguides and white light LEDs.