To date, the reported TADF-PCL materials have all showed a somewhat limited magnitude of PL spectral shift (<110 nm) upon grinding (Figure ) and there are no reports of TADF-PCL compounds exhibiting near-infrared piezochromism. In fact, to our surprise, there are only a very limited number of metal-free near-infrared piezochromic organic materials with spectral shifts greater than 150 nm reported in the literature. For instance, Zhang and co-workers reported a nearinfrared piezochromic material, MPCbZ, showing a large emission shift of 160 nm. The pristine solid (crystalline) emits at λPL of 615 nm (τPL = 4.4 ns) and has a ΦPL of 60.7% (Figure ). Grinding led to a change in morphology of the solid to an amorphous powder, emitting at λPL of 775 nm (τPL = 2.6 ns) and having a much-decreased ΦPL of 5.2%. The original photophysics could be restored upon DCM solvent fuming. Wu et al. developed a library of mechanochromic materials in which the emission of a powder sample of compound 5df switched from a λPL of 539 to 588 nm when ground and where the original emission was restored upon fuming with different solvent vapors such as those from DCM, toluene, and acetone. However, when a pressure of 14.5 GPa was applied on the crystal using a diamond anvil cell, the emission change was more dramatic, shifting from 524 to 676 nm (Figure ).