{
  "abstract": "Triplet-triplet annihilation (TTA) upconversion converts low-energy photons into higher-energy emission, but conventional TTA is limited by its two-photon nature, as the emitted photon energy cannot exceed twice the excitation photon energy. Here, a fully organic solid-state thin-film architecture cascades two TTA upconversion stages through an intermediate Förster resonance energy transfer (FRET) bridge to achieve molecular four-photon upconversion. The first sensitizer/annihilator bilayer upconverts near-infrared (NIR) excitation into intermediate singlets, which are transferred through the FRET bridge to the sensitizer of the second TTA stage. The second sensitizer/annihilator bilayer performs a second TTA step to generate blue emission. The device converts 904 nm excitation into 445 nm emission, corresponding to a 1.41 eV anti-Stokes shift and an emitted photon energy 2.03 times the excitation photon energy, exceeding the maximum possible energy gain with conventional two-photon TTA. Because two quadratic TTA stages are coupled in series, the ideal low-intensity response of the four-photon device is quartic when both stages operate below threshold, providing a steeper nonlinearity desirable for nonlinear sensing. Experimentally, power-dependent measurements reveal a superquadratic slope of 3.03, followed by quadratic and linear regimes as the constituent TTA stages cross their thresholds. Independent stage measurements and time-resolved photoluminescence dynamics support the four-photon mechanism.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Mechanical & Aerospace, Engineering, Princeton University, Princeton, New Jersey08544, United States.",
    "Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan48109, United States.",
    "Department of Electrical and Computer Engineering, Princeton University, Princeton, New Jersey08544, United States.",
    "Department of Chemistry, University of Kentucky, Lexington, Kentucky40506, United States.",
    "Department of Chemistry, North Carolina State University, Raleigh, North Carolina27695, United States.",
    "Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey08544, United States."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 10,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Seamus S Lowe"
    },
    {
      "affs": [
        1
      ],
      "name": "Maxwell Sun"
    },
    {
      "affs": [
        2
      ],
      "name": "Jesse A Wisch"
    },
    {
      "affs": [
        3
      ],
      "name": "Kostubh Gaur"
    },
    {
      "affs": [
        2
      ],
      "name": "Chiao-Jung Su"
    },
    {
      "affs": [
        4
      ],
      "name": "Azka Arshad",
      "orcid": "0000-0002-6917-2869"
    },
    {
      "affs": [
        4
      ],
      "name": "Felix N Castellano",
      "orcid": "0000-0001-7546-8618"
    },
    {
      "affs": [
        3
      ],
      "name": "John E Anthony",
      "orcid": "0000-0002-8972-1888"
    },
    {
      "affs": [
        1
      ],
      "name": "Noel C Giebink",
      "orcid": "0000-0002-3798-5830"
    },
    {
      "affs": [
        2,
        5
      ],
      "name": "Barry P Rand",
      "orcid": "0000-0003-4409-8751"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5jjnfs76gffwb.bib",
  "cited_by": 0,
  "doi": "10.1021/jacs.6c17238",
  "fulltext_url": "https://europepmc.org/articles/PMC13674276",
  "id": "5jjnfs76gffwb",
  "issns": [
    "0002-7863",
    "1520-5126"
  ],
  "landing_url": "https://europepmc.org/article/MED/42913600",
  "language": "eng",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2505|Luminescence and Fluorescent Materials"
    ]
  ],
  "openalex": "W7218893046",
  "pdf_url": "https://europepmc.org/articles/PMC13674276?pdf=render",
  "pmcid": "PMC13674276",
  "pmid": "42913600",
  "published": "2026-10-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5jjnfs76gffwb.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:14Z",
      "native_id": "MED:42913600",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42913600"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:2505|Luminescence and Fluorescent Materials",
      "subfield": "materials-polymers"
    }
  ],
  "title": "Four-Photon Molecular Upconversion.",
  "title_text": "Four-Photon Molecular Upconversion.",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:20:14Z",
  "url": "https://research.draconitic.com/paper/5jjnfs76gffwb",
  "venue": "Journal of the American Chemical Society",
  "versions": []
}