Abstract Achieving high‐efficiency thermally activated delayed fluorescence (TADF) in the solid state remains a major challenge for next‐generation optoelectronics. While molecular design strategies focus on tuning the singlet‐triplet energy gap (ΔE ST ) and spin‐orbit coupling (SOC), the role of excited‐state structural reorganization in the molecular aggregates remains largely overlooked. Here, Density Functional Theory (DFT) and Quantum Mechanics/Molecular Mechanics (QM/MM) calculations along with experimental evidence, are employed to investigate the interplay of ΔEST, SOC, and structural reorganization in both monomeric and aggregated forms of novel phenoxazine‐ and carbazole‐based luminogens. For the first time, it is revealed that low‐frequency vibrational modes (11 000 cd m −2 ). Beyond optoelectronics, the carbazole‐based emitters exhibit Mechanochromic luminescence (MCL)‐TADF with >50 nm shifts. They also show strong lipid‐droplet targeting (Pearson's r∼0.95) for bioimaging, along with efficient two‐photon upconversion. The findings render the crucial understanding for the rational design of solid‐state TADF systems, enabling efficient optoelectronic applications.
Aedelli et al. (Mon,) studied this question.