Funneling and Enhancing Upconversion Emission by Light-Harvesting Molecular Wires

Abstract

Triplet−triplet annihilation (TTA) upconversion has shown promising potentials in the augmentation of solar energy conversion. However, challenging issues exist in improving TTA upconversion efficiencies in solid-states, one of which is the back energy transfer from upconverted singlet annihilators to sensitizers, resulting in decreasing upconversion emission.Here we present a light-harvesting molecular wire consisting of dendrons with 9,10diphenylanthracene derivatives (DPAEH) at the periphery and p-phenylene ethynylene oligomers (PPE) as the wire core. The peripheral DPAEH antenna funnels singlet excitonic energy to the wire on a 12 ps time scale. Incorporating the molecular wire into the TTA upconversion solid consisting of the DPAEH annihilator and the porphyrin sensitizer evidently improves the upconversion quantum yield from 1.5% to 2.7% upon 532 nm excitation by suppressing the back energy transfer from the singlet annihilator to the sensitizer. This finding offers a potential route to use a singlet energy light-harvesting architecture for enhancing TTA upconversion.

Coupling Red‐to‐blue Upconversion Organic Microcrystals with Cd0.5Zn0.5S for Efficient and Durable Photocatalytic Hydrogen Production

“…Upconversion emission quantum yield ( Φ UC ) for each sample increases with the increase of incident power density from 11∼200 mW/cm 2 , and then it reaches a plateau between 200∼300 mW/cm 2 (Figure 1c). Φ UC for DPA/PdTPTBP microcrystals increases along with its molar ratio from 10000/1 to 100000/1, attributing to the decreased reverse energy transfer from DPA back to PdTPTBP [38–43] . The highest Φ UC (0.052±0.002) is obtained for DPA/PdTPTBP (100000/1) under intense irradiation beyond 200 mW/cm 2 .…”

“…Φ UC for DPA/PdTPTBP microcrystals increases along with its molar ratio from 10000/1 to 100000/1, attributing to the decreased reverse energy transfer from DPA back to PdTPTBP. [38][39][40][41][42][43] The highest Φ UC (0.052 � 0.002) is obtained for DPA/PdTPTBP (100000/1) under intense irradiation beyond 200 mW/cm 2 . Cd 0.5 Zn 0.5 S photocatalyst and Pt cocatalyst were prepared according to literatures (see details in Supporting Information).…”

Enhancing photon upconversion with thermally activated sensitization and singlet energy collection

“…The rise on the ps time scale is attributed to the energy transfer process from the peripheral DPA units to the PPE core and nearly unity efficiency is estimated according to the 12 ps rising time and the fluorescence lifetime of the DPA chromophores (10.8 ns). 31,38 Such a fast energy transfer with high efficiency ensures the singlet energy harvesting capability of MWDPA in TTA upconversion systems.…”

“…This strategy indeed has been proved to be effective for inhibiting FRET-type back energy transfer both in liquid and solid TTA upconversion systems. [27][28][29][30][31][32] However, an inevitable loss in the apparent anti-Stokes shift of TTA upconversion occurs due to the conventional downhill energy transfer between the annihilators and singlet energy collectors. This trade-off issue could be solved by introducing thermally activated TTA upconversion, a recently proposed mechanism involving endothermic TTET from sensitizers to annihilators, [33][34][35] where the sensitizer triplet energy level is lower than the annihilator triplet energy level and the triplet energy barrier is overcome through an endothermic TTET from the sensitizer to the annihilator during TTA upconversion.…”

Celebrating the 10th Anniversary of the Youth Innovation Promotion Association, Chinese Academy of Sciences: Emerging Young Scientists in Physical Chemistry

“…The Letter by Wang et al 16 reveals the anisotropic d−d transition in rutile TiO 2 and describes a systematic energy shift of electronic structure due to symmetry broken at the surface. Apart from these mechanism studies, this Virtual Special Issue also contains recent advances on synthesis, assembly, and applications of advanced materials, such as Ag 2 Se thermoelectric material, 17 2D metal−organic frameworks (MOFs), 18 Published: January 20, 2022 25 porous aromatic frameworks (PAFs), 26 a SiO x -based memristor, 27 a graphitelike carbon nitride nanotube, 28 α-C:H film, 29 light-harvesting molecular wires, 30 a bioresponsive zeolitic imidazolate framework (ZIF) system, 31 an M-PM 2−x -H 2 -based aqueous Zn battery, 32 and a MnO x @PAA@HKUST-1-DSF@BSA-based theranostic nanoagent. 33 The theoretical scientists in YIPA have always tried to explore high-throughput calculations to understand and design the functionality of advanced materials.…”