Heavy metal-free visible-to-UV photon upconversion with over 20% efficiency sensitized by a ketocoumarin derivative

Uji, Masanori; Harada, Naoyuki; Kimizuka, Nobuo; Saigo, Masaki; Miyata, Kiyoshi; Onda, Ken; Yanai, Nobuhiro

doi:10.1039/d1tc05526g

Cited by 26 publications

(53 citation statements)

References 45 publications

(76 reference statements)

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“…In the linear regime, the quantum efficiency is stabilized and has an average value of 12.2 ± 0.8% (Φ′ UC ; normalized to 100%) . This efficiency is slightly higher than the previous record of visible-to-UV upconversion sensitized with perovskite NCs, although it still lags behind the efficiencies achieved with molecular sensitizers. , …”

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confidence: 73%

Entropy-Powered Endothermic Energy Transfer from CsPbBr₃ Nanocrystals for Photon Upconversion

Han

Guo

et al. 2022

J. Phys. Chem. Lett.

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Colloidal semiconductor nanocrystals as triplet photosensitizers are characterized by a negligible intersystem crossing energy loss as compared to that of traditional molecular sensitizers. This property in principle allows for a large apparent anti-Stokes shift in sensitized triplet–triplet annihilation photon upconversion (TTA-UC) for a variety of applications. In previous systems, however, this advantage is largely erased by the energy loss associated with energy transfer from nanocrystals to surface-anchored triplet transmitter molecules. Here we report visible-to-ultraviolet TTA-UC from 473 to 355 nm, corresponding to an apparent anti-Stokes shift of 0.87 eV, with a quantum efficiency that reaches 4.5% (normalized at 100%). The system consists of CsPbBr3 nanocrystal sensitizers, phenanthrene transmitters, and diphenyloxazole annihilators. Time-resolved spectroscopy reveals that triplet energy transfer from CsPbBr3 nanocrystals to phenanthrene can be endothermic yet efficient thanks to a sizable entropic gain. This study exemplifies how entropic effects can be harnessed to enhance or control a plethora of applications with nanocrystals as photosensitizers.

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confidence: 73%

Entropy-Powered Endothermic Energy Transfer from CsPbBr₃ Nanocrystals for Photon Upconversion

Han

Guo

et al. 2022

J. Phys. Chem. Lett.

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“…This could potentially explain why we see a higher external Φ UC (13.1%) than that in other studies using TIPS-Naph (Φ UC ≈ 10%), in which Φ TET is reported to be close to unity. 28 , 29 …”

Section: Resultsmentioning

confidence: 99%

“… 30 The 10% limit has also been surpassed by pairing an iridium complex or a ketocoumarin derivative with 1,4-bis((triisopropylsilyl)ethynyl)naphthalene (TIPS-Naph), systems which also demonstrate low threshold excitation intensities ( I th ). 28 , 29 Other annihilators previously investigated include other naphthalene and oxazole derivatives, 8 , 30 , 36 species from the terphenyl family, 13 , 37 and as of recently also a biphenyl derivative with the capability to emit light beyond 4 eV. 38 …”

Section: Introductionmentioning

confidence: 99%

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Approaching the Spin-Statistical Limit in Visible-to-Ultraviolet Photon Upconversion

et al. 2022

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Triplet–triplet annihilation photon upconversion (TTA-UC) is a process in which triplet excitons combine to form emissive singlets and holds great promise in biological applications and for improving the spectral match in solar energy conversion. While high TTA-UC quantum yields have been reported for, for example, red-to-green TTA-UC systems, there are only a few examples of visible-to-ultraviolet (UV) transformations in which the quantum yield reaches 10%. In this study, we investigate the performance of six annihilators when paired with the sensitizer 2,3,5,6-tetra(9 H -carbazol-9-yl)benzonitrile (4CzBN), a purely organic compound that exhibits thermally activated delayed fluorescence. We report a record-setting internal TTA-UC quantum yield (Φ UC,g ) of 16.8% (out of a 50% maximum) for 1,4-bis((triisopropylsilyl)ethynyl)naphthalene, demonstrating the first example of a visible-to-UV TTA-UC system approaching the classical spin-statistical limit of 20%. Three other annihilators, of which 2,5-diphenylfuran has never been used for TTA-UC previously, also showed impressive performances with Φ UC,g above 12%. In addition, a new method to determine the rate constant of TTA is proposed, in which only time-resolved emission measurements are needed, circumventing the need for more challenging transient absorption measurements. The results reported herein represent an important step toward highly efficient visible-to-UV TTA-UC systems that hold great potential for driving high-energy photochemical reactions.

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“…TA spectroscopy TA spectra were measured by the pump-probe method [20][21][22]. For a probe pulse, we generated a white light pulse by focusing the signal light (1200 nm) from another OPA (Light Conversion, TOPAS-Prime) on a sapphire crystal (3 mm thickness).…”

Section: Steady-state Pl Spectroscopymentioning

confidence: 99%

Solvent-dependent dual emission processes in charge-transfer excited states of phenothiazine-triphenyltriazine conformers

Ryu

Miyata

Saigo

et al. 2022

Preprint

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We have investigated the solvent effects on charge-transfer excited states in a donor-acceptor type luminescent material, phenothiazine-triphenyltriazine (PTZ-TRZ), which has characteristic two conformers: quasi-axial and quasi-equatorial conformers. Solvent permittivity dependence of steady-state photoluminescence spectra using mixture solvents of toluene and tetrahydrofuran (THF) indicated that the two conformers have almost the same excited-state dipole moments. Time-resolved photoluminescence and transient absorption spectra in toluene and THF showed a different solvent dependence between the two conformers. From the detailed analysis of these time-resolved spectra, we revealed the solvent-dependent emission processes in the two conformers.

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Heavy metal-free visible-to-UV photon upconversion with over 20% efficiency sensitized by a ketocoumarin derivative

Abstract: Efficient triplet-triplet annihilation-based photon upconversion (TTA-UC) from visible to UV light without using heavy metals is still a challenging task. Here we achieve a record-high TTA-UC efficiency of 20.3% among...

Cited by 26 publications

References 45 publications

Entropy-Powered Endothermic Energy Transfer from CsPbBr₃ Nanocrystals for Photon Upconversion

Entropy-Powered Endothermic Energy Transfer from CsPbBr₃ Nanocrystals for Photon Upconversion

Approaching the Spin-Statistical Limit in Visible-to-Ultraviolet Photon Upconversion

Solvent-dependent dual emission processes in charge-transfer excited states of phenothiazine-triphenyltriazine conformers

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Heavy metal-free visible-to-UV photon upconversion with over 20% efficiency sensitized by a ketocoumarin derivative

Abstract: Efficient triplet-triplet annihilation-based photon upconversion (TTA-UC) from visible to UV light without using heavy metals is still a challenging task. Here we achieve a record-high TTA-UC efficiency of 20.3% among...

Cited by 26 publications

References 45 publications

Entropy-Powered Endothermic Energy Transfer from CsPbBr3 Nanocrystals for Photon Upconversion

Entropy-Powered Endothermic Energy Transfer from CsPbBr3 Nanocrystals for Photon Upconversion

Approaching the Spin-Statistical Limit in Visible-to-Ultraviolet Photon Upconversion

Solvent-dependent dual emission processes in charge-transfer excited states of phenothiazine-triphenyltriazine conformers

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Entropy-Powered Endothermic Energy Transfer from CsPbBr₃ Nanocrystals for Photon Upconversion

Entropy-Powered Endothermic Energy Transfer from CsPbBr₃ Nanocrystals for Photon Upconversion