Room Temperature Phosphorescence of Metal-Free Organic Materials in Amorphous Polymer Matrices

Abstract

Developing metal-free organic phosphorescent materials is promising but challenging because achieving emissive triplet relaxation that outcompetes the vibrational loss of triplets, a key process to achieving phosphorescence, is difficult without heavy metal atoms. While recent studies reveal that bright room temperature phosphorescence can be realized in purely organic crystalline materials through directed halogen bonding, these organic phosphors still have limitations to practical applications due to the stringent requirement of high quality crystal formation. Here we report bright room temperature phosphorescence by embedding a purely organic phosphor into an amorphous glassy polymer matrix. Our study implies that the reduced beta (β)-relaxation of isotactic PMMA most efficiently suppresses vibrational triplet decay and allows the embedded organic phosphors to achieve a bright 7.5% phosphorescence quantum yield. We also demonstrate a microfluidic device integrated with a novel temperature sensor based on the metal-free purely organic phosphors in the temperature-sensitive polymer matrix. This unique system has many advantages: (i) simple device structures without feeding additional temperature sensing agents, (ii) bright phosphorescence emission, (iii) a reversible thermal response, and (iv) tunable temperature sensing ranges by using different polymers.

Ion-Unquenchable and Thermally “On–Off” Reversible Room Temperature Phosphorescence of 3-Bromoquinoline Induced by Supramolecular Gels

“…Recently, Lee et al reported strong RTP induced in a solid transparent polymer (PMMA). 25,26 But the RTP was highly dependent upon the isotacticity of PMMA. In general, the preparation of highly isotactic polymers is rather difficult.…”

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“…The halogen bond [12] between different donors and PAHs/heterocyclic compounds possessing the planar large π-electron conjugation system as typical π-type acceptors can take on these tasks. Up to now, some excellent exploratory work has been reported [13,14].…”

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“…In order to decrease thermal decay and quenching by oxygen, luminescent dyes are made as crystals, or are blended into polymers [11,[17][18][19]. For example, Kim et al [20] prepared a series of organic crystals that could emit bright phosphorescence at room temperature due to halogen bonding.…”