Photochemical upconversion of near-infrared light from below the silicon bandgap

Elham M. Gholizadeh, Shyamal K.K. Prasad, Zhi Li Teh, Thilini Ishwara, Sarah Norman, Anthony J. Petty, Jared H. Cole, Soshan Cheong, Richard D. Tilley, John E. Anthony, Shujuan Huang, Timothy W. Schmidt

Research output: Contribution to journalArticlepeer-review

87 Scopus citations


Photochemical upconversion is a strategy for converting infrared light into more energetic, visible light, with potential applications ranging from biological imaging and drug delivery to photovoltaics and photocatalysis. Although systems have been developed for upconverting light from photon energies in the near-infrared, upconversion from below the silicon bandgap has been out of reach. Here, we demonstrate an upconversion composition using PbS semiconductor nanocrystal sensitizers that absorb photons below the bandgap of silicon and populate violanthrone triplet states below the singlet oxygen energy. The triplet-state violanthrone chromophores luminesce in the visible spectrum following energy delivery from two singlet oxygen molecules. By incorporating organic chromophores as ligands onto the PbS nanocrystals to improve energy transfer, we demonstrate that violanthrone upconverts in the absence of oxygen by the triplet–triplet annihilation mechanism. The change in mechanism is shown by exploiting the magnetic field effect on triplet–triplet interactions.

Original languageEnglish
Pages (from-to)585-590
Number of pages6
JournalNature Photonics
Issue number9
StatePublished - Sep 1 2020

Bibliographical note

Publisher Copyright:
© 2020, The Author(s), under exclusive licence to Springer Nature Limited.

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics


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