Abstract
To meet the world’s demands on the development of sunlight-powered renewable energy production, triplet–triplet annihilation-based photon upconversion (TTA–UC) has raised great expectations. However, an ideal highly efficient, low-power, and in-air TTA–UC has not been achieved. Here, we report a novel self-assembly approach to achieve this, which enabled highly efficient TTA–UC even in the presence of oxygen. A newly developed lipophilic 9,10-diphenylanthracene-based emitter molecule functionalized with multiple hydrogen-bonding moieties spontaneously coassembled with a triplet sensitizer in organic media, showing efficient triplet sensitization and subsequent triplet energy migration among the preorganized chromophores. This supramolecular light-harvesting system shows a high UC quantum yield of 30% optimized at low excitation power in deaerated conditions. Significantly, the UC emission largely remains even in an air-saturated solution, and this approach is facilely applicable to organogel and solid-film systems.
Highlights
Photon upconversion (UC), converting low-energy photons to higher-energy photons, is a key method for overcoming the efficiency limits of sunlight-powered devices, including photovoltaic cells and photochemical hydrogen production
In conventional triplet annihilation-based photon upconversion (TTA-UC) systems, the donor and acceptor molecules are dissolved in low-viscosity solvents, where the UC emission is largely quenched by dissolved oxygen[4,5,12,14]
The new acceptor 1 was synthesized and fully characterized, and its assembled structure in chloroform was studied by 1H NMR spectroscopy, absorption spectroscopy, and atomic force microscopy (AFM) measurements. 1H NMR spectra of 1 in deuterated chloroform (10 mM) showed amide proton signals at around 8.5, 7.2, and 6.6 ppm at 298 K, which shifted to a higher magnetic field upon heating to 333 K (Fig. 2)
Summary
Photon upconversion (UC), converting low-energy photons to higher-energy photons, is a key method for overcoming the efficiency limits of sunlight-powered devices, including photovoltaic cells and photochemical hydrogen production. Energy-migration-based UC emission has been recently reported by us and others[13,16,32,33,34,35,36,37], there exist no systems that fulfill all of the aforementioned requirements To achieve these goals, it is imperative to improve the migration rate and range of triplet excitons and to develop molecular designs for reducing the collision with oxygen molecules. The acceptor 1 self-assembles in organic media that efficiently uptake donor Pt(II) octaethylporphyrin (PtOEP) molecules, giving supramolecular donor-acceptor nanohybrids They show efficient donor-to-acceptor TTET as well as fast triplet energy migration among closely-assembled acceptors, leading to a high UC quantum yield at low excitation power. The in-air TTA-UC emission was observed in different important material forms such as gels and solid films, demonstrating the generality of the supramolecular triplet-harvesting strategy
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