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Title: Enhancing NIR-to-visible upconversion in a rigidly coupled tetracene dimer: approaching statistical limits for triplet–triplet annihilation using intramolecular multiexciton states
Important applications of photon upconversion through triplet–triplet annihilation require conversion of near-IR photons to visible light. Generally, however, efficiencies in this spectral region lag behind bluer analogues. Herein we consider potential benefits from a conformationally well-defined covalent dimer annihilator TIPS-BTX in studies that systematically compare function to a related monomer model TIPStetracene (TIPS-Tc). TIPS-BTX exhibits weak electronic coupling between chromophores juxtaposed about a polycyclic bridge. We report an upconversion yield fUC for TIPS-BTX that is more than 20× larger than TIPS-Tc under comparable conditions (0.16%). While the dimer fUC is low compared to bluer champion systems, this yield is amongst the largest so-far reported for a tetracenic dimer system and is achieved under unoptimized conditions suggesting a significantly higher ceiling. Further investigation shows the fUC enhancement for the dimer is due exclusively to the TTA process with an effective yield more that 30× larger for TIPS-BTX compared to TIPS-Tc. The fTTA enhancement for TIPS-BTX relative to TIPS-Tc is indicative of participation by intramolecular multiexciton states with evidence presented in spin statistical arguments that the 5TT is involved in productive channels. For TIPS-BTX we report a spin statistical factor f = 0.42 that matches or exceeds values found in champion annihilator systems such as DPA. At the same time, the poor relative efficiency of TIPS-Tc suggests involvement of non-productive bimolecular channels and excimeric states are suspected. Broadly these studies indicate that funneling of photogenerated electronic states into productive pathways, and avoiding parasitic ones, remains central to the development of champion upconversion systems.  more » « less
Award ID(s):
2102713
PAR ID:
10512594
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Royal Society of Chemistry
Date Published:
Journal Name:
Chemical Science
Volume:
15
Issue:
4
ISSN:
2041-6520
Page Range / eLocation ID:
1283 to 1296
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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