Nature Communications (Sep 2024)

Optically accessible long-lived electronic biexcitons at room temperature in strongly coupled H- aggregates

  • Siddhartha Sohoni,
  • Indranil Ghosh,
  • Geoffrey T. Nash,
  • Claire A. Jones,
  • Lawson T. Lloyd,
  • Beiye C. Li,
  • Karen L. Ji,
  • Zitong Wang,
  • Wenbin Lin,
  • Gregory S. Engel

DOI
https://doi.org/10.1038/s41467-024-52341-2
Journal volume & issue
Vol. 15, no. 1
pp. 1 – 9

Abstract

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Abstract Photon absorption is the first process in light harvesting. Upon absorption, the photon redistributes electrons in the materials to create a Coulombically bound electron-hole pair called an exciton. The exciton subsequently separates into free charges to conclude light harvesting. When two excitons are in each other’s proximity, they can interact and undergo a two-particle process called exciton-exciton annihilation. In this process, one electron-hole pair spontaneously recombines: its energy is lost and cannot be harnessed for applications. In this work, we demonstrate the creation of two long-lived excitons on the same chromophore site (biexcitons) at room temperature in a strongly coupled H-aggregated zinc phthalocyanine material. We show that exciton-exciton annihilation is suppressed in these H- aggregated chromophores at fluences many orders of magnitudes higher than solar light. When we chemically connect the same aggregated chromophores to allow exciton diffusion, we observe that exciton-exciton annihilation is switched on. Our findings demonstrate a chemical strategy, to toggle on and off the exciton-exciton annihilation process that limits the dynamic range of photovoltaic devices.