Diffusion-Free Intramolecular Triplet–Triplet Annihilation in Engineered Conjugated Chromophores for Sensitized Photon Upconversion

Abstract

The photon upconversion based on sensitized triplet−triplet annihilation (sTTA-UC) is a spin-flip mechanism exploited to recover the energy stored on dark triplet states in conjugated systems. In this process, a high-energy fluorescent singlet is created through the collision and fusion of two low-energy triplets belonging to different diffusing molecules. Its high yield in solution under low excitation intensity and noncoherent light highlighted the huge potential of sTTA-UC to provide a breakthrough in solar technologies. However, its diffusion-limited nature restrains its efficiency in the solid state. To overcome this issue, we propose a single-molecule system that is able to host simultaneously more than one triplet, thus enabling a diffusion-free intramolecular TTA. We obtain the first direct demonstration of intramolecular triplet fusion by tailored photoluminescence spectroscopy experiments, thus opening the way to realize a new family of single-molecule upconverters with huge potential in solar and lighting technologies by accessing the natural triplets' energy reservoir.

Nanoengineering Triplet–Triplet Annihilation Upconversion: From Materials to Real-World Applications

“…At the same time, reducing sensitizer reabsorption of UC photons must be addressed, a tricky proposition especially with UV emitting systems . Finally, continuing to engineer materials to increase photon number efficiency would be incredibly valuable to the research community (i.e., impacts of solubilizing alkyl chains, incorporation of energy funnels, and intramolecular TTA-UC ,,, ). Understanding key design principles on a molecular level to maximize performance in an “ideal” environment may enable increased light outputs in environments which reduce UC PL (e.g., embedding in a polymeric film).…”

“…Numerous tactics for increasing UC QYs have been pursued from a molecular design perspective . Molecular engineering of standalone sensitizers − and annihilators, ,, as well as covalently tethering sensitizers to annihilators ,− /annihilators to annihilators, − has been widely studied with varying degrees of success with regard to photophysical property manipulation and synthetic simplicity. Leveraging localized surface plasmon resonance (LSPR) , effects has recently been an area of intrigue.…”

Design Principles of Hybrid Nanomaterials for Radiotherapy Enhanced by Photodynamic Therapy

“…Nevertheless, the two objects should be placed at a reasonably short distance in the biological environment, a distance comparable to the diffusion length of moving charges. The drawback of this mechanism, which basically occurs in any mixture of nanoscintillators and photosensitizers, is indeed that its yield is set by the statistical probability that a photosensitizer crosses the path of a relaxing traveling charge to become its natural recombination center, which depends on the concentration and diffusivity of photosensitizers [ 97 ]. In addition, from a practical point of view, the manipulation, delivery, and localization of mixtures containing uncoupled materials is quite a difficult task.…”

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

“…This is a timely contribution given the strong interest on the use of metallorganic complexes in TTA-UC composites and organic light emitting diode devices. 80–84,100…”

“…This is a timely contribution given the strong interest on the use of metallorganic complexes in TTA-UC composites and organic light emitting diode devices. [80][81][82][83][84]100 A set of material characterization experiments is applied on a range of composition dependent DPA:PtOEP composite lms developed by solution processing. Grazing incidence X-ray diffractometry (GIXRD) measurements identify the dominant DPA polymorph in the DPA:PtOEP lms.…”