Picosecond time-resolved antibunching measures nanoscale exciton motion, annihilation, and true number of chromophores

TL;DR

This paper introduces picosecond time-resolved antibunching (psTRAB), a novel technique to analyze nanoscale exciton dynamics, including diffusion, annihilation, and the true number of chromophores, at the single-particle level.

Contribution

The study develops psTRAB to accurately decode exciton processes and measure chromophore numbers and diffusion rates in complex multichromophoric systems.

Findings

Measured true number of chromophores on DNA origami structures.

Determined distance-dependent exciton annihilation rates.

Distinguished intra-chain and inter-chain exciton diffusion modes.

Abstract

The particle-like nature of light becomes evident in the photon statistics of fluorescence of single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here, we develop picosecond time-resolved antibunching (psTRAB) to identify and decode such processes. We use psTRAB to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, psTRAB allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a new lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles, and materials for optoelectronic devices.