@article{Goudarzi:2019:10.1039/C8TC06283H,
author = {Goudarzi, H and Limbu, S and Cabanillas-González, J and Zenonos, VM and Kim, J-S and Keivanidis, PE},
doi = {10.1039/C8TC06283H},
journal = {Journal of Materials Chemistry C},
pages = {3634--3643},
title = {Impact of molecular conformation on triplet-fusion induced photon energy up-conversion in the absence of exothermic triplet energy transfer},
url = {http://dx.doi.org/10.1039/C8TC06283H},
volume = {7},
year = {2019}
}

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TY  - JOUR
AB  - 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) PtII (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 DPtOEP = 4.1 × 10−9 cm2 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. Th
AU  - Goudarzi,H
AU  - Limbu,S
AU  - Cabanillas-González,J
AU  - Zenonos,VM
AU  - Kim,J-S
AU  - Keivanidis,PE
DO  - 10.1039/C8TC06283H
EP  - 3643
PY  - 2019///
SN  - 2050-7526
SP  - 3634
TI  - Impact of molecular conformation on triplet-fusion induced photon energy up-conversion in the absence of exothermic triplet energy transfer
T2  - Journal of Materials Chemistry C
UR  - http://dx.doi.org/10.1039/C8TC06283H
UR  - http://hdl.handle.net/10044/1/66976
VL  - 7
ER  - 

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