Blue‐Green Up‐Conversion: Noncoherent Excitation by NIR Light

Abstract

An emitter/sensitizer couple (see picture; C red/green, H white, N blue, Pd gray) was specially designed for the process of noncoherently excited photon up‐conversion. The hypsochromic shift between the energy of the excitation photons and the emitted photons is about 0.7 eV, and an external quantum yield of 0.04 is achieved. As noncoherent excitation source, the near‐infrared part of the solar spectrum was used.

Visible‐Light Harvesting with Cyclometalated Iridium(III) Complexes Having Long‐Lived 3IL Excited States and Their Application in Triplet–Triplet‐Annihilation Based Upconversion

“…The dyads are weakly phosphorescent (Φ P = 0.6 %); however, we proved that the triplet excited states of the Ir III complexes are efficiently populated upon photoexcitation, by using the complexes as triplet sensitizers for triplet-triplet annihilation upconversion. [21][22][23][24] Upconversion quantum yields (Φ UC ) of up to 23.4 % were observed, whereas Φ UC = 0.0 % for Ir-1 and Ir-2 (two complexes without the visible-light harvesting effect) under the same experimental conditions. between the coumarin unit and the imidazole-Phen unit, to investigate the potential effect of the intramolecular hydrogen bond in the ligand of Ir-3.…”

“…[21] Upconversion (UC) is important for photovoltaics, photocatalysis, and nonlinear photonics. [24,31,32] Among UC applications, such as two-photon absorption dyes, nonlinear optical crystals, or rare earth metal materials, [33] TTA upconversion is particularly interesting, because of its low excitation power (can be lower than the energy of solar light) and its readily adjustable excitation/emission wavelengths. [21][22][23][24] However, we note the limitations facing the current development of TTA upconversion, such as the limited availability of triplet sensitizers, which are currently limited to Ru II polyimine complexes [34] and Pt II /Pd II porphyrin complexes.…”

“…Herein we selected upconversion based on triplet-triplet-annihilation (TTA), [21][22][23][24] which requires triplet sensitizers to harvest excitation light and transfer the energy to a triplet acceptor (see Jablonski diagram, Scheme 2, for photophysical details). [21] Upconversion (UC) is important for photovoltaics, photocatalysis, and nonlinear photonics.…”

Photon Upconversion on Dye-Sensitized Nanostructured ZrO2 Films

“…1 A main reason behind this renewed interest is the fact that UC-STTA can occur under sunlight-like conditions, namely, low-intensity, noncoherent excitation light, 2 so that it is potentially useful in photovoltaics. UC-STTA can be described as follows (see Scheme 1): A sensitizer molecule, S, typically an inorganic complex with highly efficient intersystem crossing, absorbs a low-energy photon and stores the excitation energy in a long-lived triplet state S þ hν low f 1 S Ã ð1Þ…”

A Versatile General Approach to the Synthesis of Linearly Annelated π-Extended Porphyrins via 4,7-Dihydroisoindole Derivatives

“…[6] Platinum complex of tetraphenyltetranaphthoporphyrin was recently shown to exhibit record efficiency in near-infrared OLED devices. [7] In addition, the Pd and Pt complexes of LAEP have recently been demonstrated to be unique light harvesting materials for two-photon up-conversion based on triplet-triplet annihilation, allowing to transform low-intensity non-coherent red and near infrared light into shorter wavelength visible light, [8] spawning applications for all-organic flexible displays [9] and solar cell efficiency enhancement. [10] A few synthetic approaches to such systems were developed, including the template condensation, [11,12,13] Ono's method using the ethane-bridged tetrahydroisoindoles [14,15] and the tetrahydroisoindole approach.…”