The observed emission variations in the solid state can be attributed to TSCT interactions between the PAM donors and the NDI acceptor. A higher PAM loading may lead to a closer overall proximity between NDI and PAM, resulting in enhanced charge-transfer (CT) transitions of NDI-PAM pairs in comparison to those of NDI scaffold or NDI-styrene pairs. Intriguingly, NDI-coVPy, NDI-coPyMA, NDI-coAntMA, and NDI-coAntMAc exhibited bimodal fluorescence with large redshifts (140-190 nm) with the increase of PAM feed, similar to the aggregationenhanced FRET emission spectra despite the difference in D-A distance (< 1 nm in TSCT versus < 10 nm in FRET ). The TSCT-induced emissions could only be observed in aggregate states (powders, films or aqueous aggregates) with typical AIE activities (Figures and). This further confirmed that the TSCT occurs only when the donor and acceptor are spatially close to one another . Importantly, the characteristic emission redshift in each NDI-copolymer derives from the specific D-A (PAM-NDI) interactions, depending on the PAM's electrondonating ability (as indicated in Table ). By introducing the donor groups with a controlled fraction via copolymerization strategy, it was possible to achieve continuous color tuning via simple manipulation of the degree of D-A charge transfer. Figures 3A and 3B summarize the PL emission properties of NDI-polystyrene (PS) and NDI-copolymers at the highest PAM feed, showing full-color tunability from sky blue to deep red with emission spectra spanning from 400 to 800 nm. The characteristic emission redshift is a result of the diverse CT excited state formed between NDI and the donor PAM with a distinct degree of π-conjugation. With increasing π-conjugation degree of PAM, the fluorescence lifetime of NDI-copolymers decreased from 37.6 to 7.1 ns (Figure and Table ), indicating the characteristic TSCT excited state of each copolymer. In addition, all NDI-copolymers showed characteristic NDI absorption at ~360 and ~380 nm (Figure ), whereas NDI-coVPy and NDI-coPyMA exhibited strong absorption peaks at ~330 and ~350 nm from pyrene groups. Slight red shifts at the tail end of the absorption spectra were observed in the polymer aggregates in aqueous solutions in comparison to the spectra of the dissolved polymers, further indicating the TSCT interactions (Figure ).