Research ArticleChemistry

Allochroic thermally activated delayed fluorescence diodes through field-induced solvatochromic effect

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Science Advances  15 Sep 2017:
Vol. 3, no. 9, e1700904
DOI: 10.1126/sciadv.1700904
  • Scheme 1 Strategy of allochroic TADF diodes.

    (A) Allochroic mechanism of dyes with CT excited states in polar matrices known as solvatochromism. (B) Design strategy of allochromic TADF diodes based on host matrix with voltage-dependent polarity.

  • Fig. 1 Molecular design of tBCzHxPO host with transformable binary polar states.

    (A) Single-crystal structures of tBCzHxPO, indicating the preferential endo structures with IHBs at thermodynamic stable states. (B) Conformation transformation between exo- and endo-type isomers of tBCzHxPO driven by hydrogen bond formation and the resulted polarity and energy variation. (C) EL spectra of tBCzHxPO-based OLEDs in a voltage range of 5.5 to 9.5 V with an interval of 0.5 V. (D) Photoluminescence (PL) spectra (inset) and time decay curves of emissions from vacuum-evaporated DMAC-DPS–doped tBCzHxPO and tBCzMxPO thin films [100-nm thickness, 10 weight % (wt %)].

  • Fig. 2 EL performance of tBCzHxPO- and tBCzMxPO-based TADF diodes.

    (A) Configurations of TADF devices using DMAC-DPS as a dopant and the chemical structures of the used materials. (B) Luminance–current density–voltage characteristics of the devices. (C) Efficiency versus luminance curves of the devices. (D) Comparison on EL spectra of the devices on the operation voltages by a range of 3.5 to 10 V. (E) CIE chromaticity coordinate variation of tBCzHDPO-based devices along with a voltage increase from 3.5 to 10 V. The schematic illustration shows the mechanism of emission color change, namely, electro-solvatochromism, through polarity reduction of tBCzHDPO from its exo- to endo-type conformers.

  • Fig. 3 Nonvolatile visible information storage by tBCzHDPO-based allochroic TADF diodes.

    (A) Dependence of EL spectra on driving voltage during the first and second increasing processes from 4 to 8 V. (B) Schematic illustration of memory process: Data are read at low voltage with an emission detector and written at high voltage for emission color change. (C) Images of six-pixel devices as a typical binary memory unit. Inset shows the driving circuit. Two memories show visible information of “000111” and “101010” (inset) at 4 V. (D) Data storage stability of the write-once read–many times (WORM) devices during multiple read processes.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/9/e1700904/DC1

    Experimental section

    Gaussian simulation results

    Optical properties of the PO molecules

    Thermal and morphological properties of tBCzHxPO

    Electrical properties of tBCzHxPO

    Polarity variation of tBCzMxPO isomers

    Device structure and electroluminescence process

    Encryption mechanism

    Device performance

    Movie indicating the allochroic process

    scheme S1. Synthetic procedure of tBCzHxPO.

    scheme S2. Device structure and energy level diagram of the devices.

    scheme S3. Encryption flow chart of EWPR-type memory based on irreversible AOLEDs.

    fig. S1. Potential variation during conformation transformation of tBCzHxPO.

    fig. S2. Involved molecular orbitals, contours, and contribution weights of S0→S1 transitions for tBCzHxPO and tBCzMxPO simulated by the NTO method.

    fig. S3. Energy levels and contours of FMOs for tBCzHxPO.

    fig. S4. Photophysical properties of tBCzHxPO and tBCzMxPO.

    fig. S5. Thermal and morphological properties of tBCzHxPO.

    fig. S6. Electrical properties of tBCzHxPO.

    fig. S7. Conformations of exo- and endo-type tBCzMxPO and the resulted polarity and energy variation during transformation by DFT and TDDFT simulations.

    fig. S8. EQE versus luminance curves of the devices.

    fig. S9. Correlations between emission peaks, driving voltage, operation time, and power density.

    fig. S10. Performance repeatability of the allochroic TADF devices.

    fig. S11. 1H nuclear magnetic resonance (NMR) spectrum of tBCzHSPO.

    fig. S12. 13C NMR spectrum of tBCzHSPO.

    fig. S13. 31P NMR spectrum of tBCzHSPO.

    fig. S14. 1H NMR spectrum of tBCzHDPO.

    fig. S15. 13C NMR spectrum of tBCzHDPO.

    fig. S16. 31P NMR spectrum of tBCzHDPO.

    table S1. Physical properties of tBCzHxPO.

    table S2. EL performance of DMAC-DPS–based devices.

    movie S1. Allochroic TADF diode.

    References (3438)

  • Supplementary Materials

    This PDF file includes:

    • Experimental section
    • Gaussian simulation results
    • Optical properties of the PO molecules
    • Thermal and morphological properties of tBCzHxPO
    • Electrical properties of tBCzHxPO
    • Polarity variation of tBCzMxPO isomers
    • Device structure and electroluminescence process
    • Encryption mechanism
    • Device performance
    • Movie indicating the allochroic process
    • scheme S1. Synthetic procedure of tBCzHxPO.
    • scheme S2. Device structure and energy level diagram of the devices.
    • scheme S3. Encryption flow chart of EWPR-type memory based on irreversible AOLEDs.
    • fig. S1. Potential variation during conformation transformation of tBCzHxPO.
    • fig. S2. Involved molecular orbitals, contours, and contribution weights of S0→S1 transitions for tBCzHxPO and tBCzMxPO simulated by the NTO method.
    • fig. S3. Energy levels and contours of FMOs for tBCzHxPO.
    • fig. S4. Photophysical properties of tBCzHxPO and tBCzMxPO
    • fig. S5. Thermal and morphological properties of tBCzHxPO.
    • fig. S6. Electrical properties of tBCzHxPO.
    • fig. S7. Conformations of exo- and endo-type tBCzMxPO and the resulted polarity and energy variation during transformation by DFT and TDDFT simulations.
    • fig. S8. EQE versus luminance curves of the devices.
    • fig. S9. Correlations between emission peaks, driving voltage, operation time, and power density.
    • fig. S10. Performance repeatability of the allochroic TADF devices.
    • fig. S11. 1H nuclear magnetic resonance (NMR) spectrum of tBCzHSPO.
    • fig. S12. 13C NMR spectrum of tBCzHSPO.
    • fig. S13. 31P NMR spectrum of tBCzHSPO.
    • fig. S14. 1H NMR spectrum of tBCzHDPO.
    • fig. S15. 13C NMR spectrum of tBCzHDPO.
    • fig. S16. 31P NMR spectrum of tBCzHDPO.
    • table S1. Physical properties of tBCzHxPO.
    • table S2. EL performance of DMAC-DPS–based devices.
    • Legend for movie S1
    • References (34–38)

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1. (.mov format). Allochroic TADF diode.

    Files in this Data Supplement:

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