Solid State Photon Up-Conversion Emission from Chromophore-Tethered PPV Films

Abstract

Solid state triplet–triplet annihilation (TTA) upconversion (UC) systems may find application as elements in a wide range of practical photon energy conversion technologies. One strategy to produce highly efficient UC emission in the solid state is to create systems that can efficiently transport generated triplets to distances significantly longer than afforded by the Dexter mechanism under restriction of molecular movement. In this work, we present a new solid state UC system through integration of conjugated poly­(p-phenylene vinylene) (PPV) derivatives, with tethered and/or blended chromophores of (9,10-bisphenylethynylanthracene (BPEA) as an emitter and palladium­(II) meso-tetraphenyltetrabenzoporphyrine (TBP)) as a sensitizer. Photoluminescence spectroscopy reveals that the introduction of a small ratio (ca. 3%) of covalently bound BPEA onto the PPV backbone enhances UC emission around an order of magnitude compared to the homo-PPV when mixed with 2 wt % TBP. On the other hand, time-resolved measurements find more rapid consumption of the generated sensitizer triplets with BPEA increased concentrations (up to 50 mol %), suggesting that these BPEA units provide accelerated triplet energy transfer (TET) compared to in homo-PPV, however there exists a significant loss channel via energy back transfer in PPV-BPEA with higher contents of the BPEA unit. Moreover, microsecond time scale decay behavior, where a small population of triplets exist, show that triplets were mainly transmitted through the conjugated polymer phase.

Challenges, progress and prospects in solid state triplet fusion upconversion

“…Mori et al have also investigated PPV derivatives by conjugating an additional chromophore unit, the 9,10-bisphenylethynylanthracene (BPEA) as an annihilator, and used palladium( ii ) meso -tetraphenyltetrabenzoporphyrine (TBP) as a sensitizer. 77 Their results suggest that the covalently bound BPEA units increase the TET rate in comparison with pure PPV, while also being a source of energy loss due to energy back transfer at a high BPEA ratio.…”

Recent advances of triplet–triplet annihilation upconversion in solvent-free solid materials

“…32 Using polystyrene derivatives (PPV) as the polymer matrix and the selection of PdTBP as the photosensitizer molecule, BPEA as the acceptor molecule was reported by Nattestad's group in 2021. 37 The authors used a copolymerization method to link the photosensitizer and acceptor molecules on a polystyrene molecule, with the polymer serving as the exciton transfer medium. It was found that the introduction of a small ratio ( ca.…”

Microstructure-driven annihilation effects and dispersive excited state dynamics in solid-state films of a model sensitizer for photon energy up-conversion applications

“…[6][7][8][9][10][11][12][13] Owing to their easily executable and inexpensive processing protocols, solution processable TTA-UC solid-state mixtures prepared by using small molecular and macromolecular p-conjugated systems are ideal candidate systems to be used as TTA-UC interlayers for device applications. [14][15][16] The solution processable character of TTA-UC organic materials offers an attractive opportunity to complement the portfolio of other existing photon energy up-converting systems [17][18][19][20][21] and to avoid disruptions in the design of currently employed device architectures. Although the realization of TTA-UC layers as functional device components is lagging, encouraging results were recently presented on a green-to-blue model TTA-UC composite prepared by blending the greenabsorbing (2,3,7,8,12,13,17,18-octaethyl-porphyrinato) Pt II (PtOEP) square-planar sensitizer with the blue-light emitting 9,10 diphenyl anthracene (DPA) emitter, a polycyclic aromatic hydrocarbon derivative.…”