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Schiff bases are a crucial component in various functional materials but often exhibit non‐emissive behavior which significantly limits their potential applications as luminescent materials. However, traditional approaches to convert them into aggregate emitters often require intricate molecular design, tedious synthesis, and significant time and resource consumption. Herein, we present a cocrystallization‐induced emission strategy that can transform non‐emissive (hetero)aryl‐substituted Schiff bases into green‐yellow to yellow aggregate emitters via even simple grinding of a mixture of Schiff bases and 1,2,4,5‐tetracyanobenzene (TCB) mixtures. The combined experimental and theoretical analysis revealed that the cocrystallization inhibits the C=N isomerization and promotes face‐to‐face π–π interaction, which restricts access to both the dark state and canonical intersection to ultimately induce emission. Furthermore, the induced emission enables the observation of solid‐state molecular diffusion through fluorescence signals, advancing white light emission diodes, and notably, solution‐processed organic light‐emitting diodes based on cocrystal for the first time. This study not only highlights the potential of developing new C=N structural motifs for AIEgens but also could boost advancements in related structure motifs like C=C and N=N. [ABSTRACT FROM AUTHOR]

The combination of acridine-based spiro donors of benzophenone acceptor furnishes efficient delayed fluorescence luminogens with high photoluminescence efficiencies, large horizontal dipole ratios and balanced bipolar carrier transport, proving brilliant electroluminescence efficiencies of up to 32.2% and small efficiency roll-offs. [Display omitted] • Robust green delayed fluorescence luminogens are designed and synthesized. • Spiro electron donors promote the horizontal orientation of emitting dipoles. • High-performance organic light-emitting diodes are achieved with the luminogens. Developing high-performance organic light-emitting diodes (OLEDs) with high external quantum efficiency (η ext) and low efficiency roll-off is an unremitting goal, which greatly relies on the exploration of robust luminescent materials. Herein, we report a series of new delayed fluorescence luminogens built with acridine-based spiro donors and benzophenone acceptor. These luminogens have distinct merits of excellent thermal stability, aggregation-enhanced delayed fluorescence, high photoluminescence quantum yields, preferable horizontal dipole orientation and balanced bipolar charge transport. The presence of spiro donors endows the luminogens with large horizontal orientation ratios and thus high light out-coupling efficiencies. The OLEDs based on these luminogens radiate intense green light (504–512 nm) and furnish outstanding η ext values of up to 32.2% and small efficiency roll-offs, which are among the state-of-the-art delayed fluorescence OLEDs with η ext s over 30%, demonstrating their great potentials in the fabrication of highly efficient OLEDs. [ABSTRACT FROM AUTHOR]