Please use this identifier to cite or link to this item:
|Title:||Impact of molecular conformation on triplet-fusion induced photon energy up-conversion in the absence of exothermic triplet energy transfer||Authors:||Goudarzi, Hossein
Zenonos, Vassiliki M.
Keivanidis, Panagiotis E.
|Keywords:||Energy transfer;Photoluminescence spectroscopy;Spectroscopic analysis;Absorption spectroscopy||Category:||Environmental Engineering||Field:||Engineering and Technology||Issue Date:||2019||Source:||Journal of Materials Chemistry C, 2019, Volume 7, Issue 12, Pages 3634-3643||Journal:||Journal of Materials Chemistry C||Abstract:||The use of photon energy up-converted luminescence driven by triplet-exciton annihilation reactions (TTA-UC) is increasingly gaining attention for developing next-generation light-management, and wavelength-shifting technologies. Here we present a spectroscopic study for elucidating the photophysical mechanism that operates in an unusual TTA-UC model system comprising the blue-light emitting poly(fluorene-2-octyl) (PFO) activator mixed with the green-light absorbing (2,3,7,8,12,13,17,18-octaethyl-porphyrinato) Pt II (PtOEP) metalo-organic complex. The unconventional character of the PFO:PtOEP composite manifests in the fact that no exothermic triplet energy transfer (TET) is possible between triplet-excited PtOEP and PFO. Yet green-to-blue TTA-UC luminescence of PFO is obtained even when PtOEP is selectively photoexcited by pulsed laser intensities as low as 2.5 mW cm −2 . Continuous-wave photo-induced absorption spectroscopy verifies that no energy transfer from triplet-excited PtOEP to the triplet level of PFO takes place, pointing to triplet-triplet annihilation (TTA) events in the PtOEP phase as the origin of the observed TTA-UC PL signal. In the PFO:PtOEP composite, the PtOEP component holds a dual role of annihilator/sensitizer; photon energy storage in PtOEP is enabled via TTA when triplet exciton diffusion coefficient values of D PtOEP = 4.1 × 10 −9 cm 2 s −1 are reached. With a simple yet powerful solution processing protocol, and by combining Raman and time-gate photoluminescence (PL) spectroscopy we demonstrate that the brightness of the produced TTA-UC luminescence depends on the molecular conformation of the PFO activator. A four-fold increase in the TTA-UC luminescence intensity is registered in the time-integrated and time-gated PL spectra, when the PFO matrix is arrested in its planar β-phase molecular conformation. Further enhancement of the TTA-UC PL signal is achieved when temperature lowers from 290 K down to 100 K. These results stimulate the development of a theoretical model for the microscopic description of triplet exciton migration in disordered photon up-converting solids. Efficient harvesting of photon energy, which is stored in annihilator/sensitizer moieties via TTA events, can be enabled when the molecular conformation of the activator species is properly tuned.||URI:||http://ktisis.cut.ac.cy/handle/10488/13697||ISSN:||2050-7534||DOI:||10.1039/c8tc06283h||Rights:||© The Royal Society of Chemistry.||Type:||Article|
|Appears in Collections:||Άρθρα/Articles|
Show full item record
WEB OF SCIENCETM
checked on Sep 14, 2019
checked on Sep 19, 2019
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.