Piezochromism or piezochromic luminescence (PCL) has been extensively investigated in numerous organic semiconductor materials. Of these, a subset emit via thermally activated delayed fluorescence (TADF). TADF compounds typically possess highly twisted donor-acceptor conformations, which ensures that there is a sufficiently small singlet-triplet energy gap, DEST, to enable reverse intersystem crossing at ambient temperatures. Piezochromic TADF compounds also engage in weak non-covalent intermolecular interactions and thus their optical properties are most likely to respond to external mechanical stimulus. For instance, Xie et al. reported CPzPO and SPzPO that showed a dual emission in the crystalline state (λPL of 459 nm and 564 nm for CPzPO and 433 nm and 546 nm for SpzPO). After grinding, the lower energy emission band was enhanced while the higher energy emission band disappeared for both compounds, which is due to a crystalline to amorphous material transition. The lower energy band had TADF behavior, with τd of 62 and 29 μs, for CPzPO and SPzPO, respectively. Zhou et al. reported a tetracoordinate boron-based TADF emitter R-DOBP (ΦPL of 11% and τd of 6 μs in the neat film). This compound showed a red-shifted emission from 580 nm to 647 nm upon grinding, caused by a crystalline to amorphous material transition. Swager and co-workers reported a through space charge transfer TADF emitter XPT that showed a change in lPL from 536 nm to 569 nm upon grinding, the original emission could be restored upon DCM solvent fuming. XPT emits at lPL of 566 nm, has a ΦPL of 66% and a τd of 3.3 µs in 10 wt% doped films in DPEPO. An organic light-emitting diode (OLED with XPT showed an EQEmax of 10% at λEL of 584 nm.