Crystallization, clustering, matrix rigidification, deuteration, and polymerization strategies have each been employed to suppress molecular motion that is a primary conduit for nonradiative decay. For example, Bolton et al. achieved high-efficiency RTP with a phosphorescence quantum yield (FPh) of 55% via crystallization of brominated aromatic compounds. In a similar vein, Hamzehpoor et al. developed covalent organic frameworks (COFs) that showed efficient RTP by copolymerization of halogenated and unsubstituted phenyldiboronic acids. By controlling the halogen doping concentration in this rigid two-dimensional material, a ΦPh = 29 % was obtained for BrCOF-7. Intermolecular subunit interlocking mediated by the sodium cations in poly(styrene sulfonic acid) sodium (PSSNa) polymers was reported by Cai et al. to reduce non-radiative decay, turning on RTP having a FPh of 5.3%. Hirata et al. demonstrated that deuteration is a tool to decrease both radiative and non-radiative rates by reducing the Frank-Condon factor, exemplified in deuterated N,N′-diphenyl-N,N′-(3-methyl phenyl)-1,1′-biphenyl-4,4′-diamine (TPD), which showed an improved ΦPh of 6.2% doped in β-estradiol compared with that of 3.0% for the original TPD. Ren et al. documented that RTP (ΦPh = 1.3%) can be triggered by the clustering of poly (1,4- dihydropyridine)s polymers in benzophenone. Hydrogen bonding interactions can also be used to produce immobilized emitter molecules within a host matrix, such as in so-called hydrogen-bonded organic frameworks (HOFs). Host-guest hydrogen bonding has been demonstrated as an effective way to suppress triplet non-radiative transitions. For instance, Kown et al. reported that films of carboxylic acid-decorated bromoaldehyde (G1, Figure ) doped in poly(vinyl alcohol) (PVA) as the matrix have a FPh of 24%. Xiong et al. achieved tuneable afterglows by doping different pyridine-substituted triphenylamines, TPA-Py, TPA-2Py, and TPA-3Py (Figure ), into PVA, where the TPA-3Py@PVA showed the highest FPh of 15.2% coupled with a phosphorescence lifetime (tPh) of ~800 ms. The different hydrogen bonding interactions between guest phosphors and PVA impacted the tPh, which were all on the order of a second. Wu and co-workers reported blue RTP (lPh= 463 nm, FPh = 34.7%) by embedding aromatic (P3, Figure ) in PVA. From these examples and the diversity of the guest chemical structure, it seems that PVA can serve as a suitable host to turn on RTP. Beyond this matrix, other hydrogen-bonding matrices have been employed to enable RTP.