Research ArticleAPPLIED SCIENCES AND ENGINEERING

Programmable transparent organic luminescent tags

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Science Advances  01 Feb 2019:
Vol. 5, no. 2, eaau7310
DOI: 10.1126/sciadv.aau7310
  • Fig. 1 Energetic scheme, device structure, and emission with and without oxygen quenching.

    (A) Electron excitation by UV light to the excited singlet state S1 of NPB with following fluorescence or ISC to the excited triplet state T1. (B) NPB T1 state depopulation in the presence of oxygen via triplet-triplet interaction with molecular oxygen and therefore excited singlet oxygen generation. (C) Blue fluorescent emission in continuous wave (CW) excitation, no delayed phosphorescence in the presence of oxygen. (Photo credit: F.F., Dresden Integrated Center for Applied Physics and Photonic Materials). (D) Device structure. The emitting- and barrier-layer thicknesses are 900 and 600 nm, respectively. (E) NPB T1 state depopulation without surrounding oxygen via visible phosphorescence with a lifetime of τ = 406 ms. (F) Blue fluorescent emission in continuous wave excitation and delayed response in the absence of oxygen. Greenish-yellow phosphorescence is visible.

  • Fig. 2 Overview of writing, reading and erasing procedure.

    (A) Writing: Masked UV illumination used for the images in (E) and proposed straight laser ray writing. (B) Different spectral domains used for different cycle steps. Data writing is realized with a 365-nm LED, the biluminophore emits at 420 nm (fluorescence) and 530 to 570 nm (phosphorescence). IR light peaking at 4 μm is uSsed for erasing. Note that the IR spectrum is calculated from black-body radiation at 490°C. (C) Reading: High luminescent contrast is achieved by phosphorescence on mask-illuminated areas in delayed emission. (D) Erasing: By heating the sample through IR illumination, the programming is erased within around 1 min. (E) Different phosphorescent images written successively onto the same transparent substrate. The time span between the afterglow images is about 5 min.

  • Fig. 3 Dynamics of emerging and disappearing phosphorescence.

    (A) Normalized phosphorescent intensity of freshly prepared samples as a function of illumination time for different UV intensities ranging from 0.1 to 7.0 mW cm−2. (B) Illumination intensity dependences of required time to reach 50% of total phosphorescent emission. The black line is a power-law fit using an exponent of −1. (C) Normalized phosphorescence as a function of storage time for two different film thicknesses, 600 nm (light red circles) and 35 to 40 μm (dark red squares), stored and measured under ambient conditions. The emission increase at the beginning is reproducible and under further investigation. (D) Normalized phosphorescence as a function of heating time. Heated at 50°C, a spin-coated barrier layer leads to the loss of phosphorescence after 10 to 20 s. At this temperature, a thick drop-casted barrier layer retains phosphorescence for more than 160 s. Heated at 95°C, the same sample shows the full loss of phosphorescence after 20 to 40 s.

  • Fig. 4 Coatings on different substrates.

    (A) Flexible luminescent tag realized by spin-coating the emitting layer in between two barrier films in ambient light and showing written phosphorescence. (B) Flexible adhesive tag applied to a cylindrical glass bottle and containing information about the content, readable by eye and any quick response (QR) detector, and fully invisible when not read out. (C) Conventional monochrome photograph coated by drop-casting the emitting layer in between two barrier layers showing a programmable luminescent caption. (D) Transmission of an emitting layer similar to the one on top of the photo in (C) compared to 1-mm pure glass.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/2/eaau7310/DC1

    Fig. S1. Oxygen consumption effects in solutions and films containing PMMA and NPB.

    Fig. S2. Phosphorescence decay of PMMA:NPB (2 wt %) covered by an oxygen barrier.

    Fig. S3. USAF 1951 test target and achieved maximum resolution.

    Fig. S4. Writing and erasing cycles and resulting degradation processes.

    Fig. S5. Different coating methods on different substrate materials.

    Movie S1. Image writing using UV light.

    Movie S2. Image reading using UV light.

    Movie S3. Writing, reading, and erasing different patterns.

    Movie S4. Image writing using UV light (original video).

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Oxygen consumption effects in solutions and films containing PMMA and NPB.
    • Fig. S2. Phosphorescence decay of PMMA:NPB (2 wt %) covered by an oxygen barrier.
    • Fig. S3. USAF 1951 test target and achieved maximum resolution.
    • Fig. S4. Writing and erasing cycles and resulting degradation processes.
    • Fig. S5. Different coating methods on different substrate materials.
    • Legends for movies S1 to S4

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Image writing using UV light.
    • Movie S2 (.mp4 format). Image reading using UV light.
    • Movie S3 (.mp4 format). Writing, reading, and erasing different patterns.
    • Movie S4 (.mp4 format). Image writing using UV light (original video).

    Files in this Data Supplement:

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