Design Guidelines for Rigid Epoxy Resins with High Photon Upconversion Efficiency: Critical Role of Emitter Concentration

Tsubasa Kashino, Rena Haruki, Masanori Uji, Naoyuki Harada, Masanori Hosoyamada, Nobuhiro Yanai, Nobuo Kimizuka

Research output: Contribution to journalReview articlepeer-review

6 Citations (Scopus)


For the practical application of triplet-triplet annihilation-based photon upconversion (TTA-UC), the development of rigid, transparent, air-stable, and moldable materials with a high TTA-UC efficiency remains a challenging issue. In addition to the noncovalent introduction of ionic liquid emitters into the epoxy network, we covalently introduce emitters with polymerization sites to increase the emitter concentration to 35.6 wt %. A TTA-UC quantum yield φUCof 5.7% (theoretical maximum: 50%) or a TTA-UC efficiency ηUCof 11.4% (theoretical maximum: 100%) is achieved, which is the highest value ever achieved for a rigid polymer material. More importantly, the high emitter concentration speeds up the triplet diffusion and suppresses the back energy transfer from the emitter to sensitizer so that the sensitized emitter triplet can be effectively utilized for TTA. The generality of our finding is also confirmed for epoxy resins of similar emitter unit concentrations without the ionic liquid. This work provides important design guidelines for achieving highly efficient TTA-UC in rigid solid materials, which has been very difficult to achieve in the past. Furthermore, the solid-state TTA-UC exhibits high air stability, reflecting the high oxygen barrier performance of epoxy resins. The high moldability of epoxy resins allows the construction of upconversion materials with complex geometries at nano- to macroscopic scales.

Original languageEnglish
Pages (from-to)22771-22780
Number of pages10
JournalACS Applied Materials and Interfaces
Issue number20
Publication statusPublished - May 25 2022

All Science Journal Classification (ASJC) codes

  • General Materials Science


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