Diffusion-free photon upconversion driven by intramolecular triplet-triplet annihilation in engineered conjugated chromophores

TL;DR

This paper introduces a novel diffusion-free photon upconversion method using intramolecular triplet-triplet annihilation in engineered conjugated chromophores, overcoming the limitations of traditional diffusion-dependent processes for improved solar and lighting applications.

Contribution

The authors designed molecular systems capable of hosting multiple triplets, enabling intramolecular TTA and demonstrating this process through tailored photoluminescence spectroscopy.

Findings

First direct demonstration of intramolecular triplet fusion

Potential for high-efficiency single-molecule upconverters

Overcomes diffusion limitations in solid-state upconversion

Abstract

The photon upconversion based on sensitized triplet-triplet annihilation (sTTA-UC) is a spin-flip mechanism exploited to recover the energy of 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 excellent yield in solution under low excitation intensity and non-coherent light highlighted the huge potential of sTTA-UC to provide a breakthrough in solar technologies. However, its diffusion-limited bi-molecular nature limits its efficiency in the solid state. To overcome this issue, we designed a molecular systems 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 lightening technologies by accessing the natural triplets energy reservoir.