Research ArticleChemistry

Engendering persistent organic room temperature phosphorescence by trace ingredient incorporation

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Science Advances  07 May 2021:
Vol. 7, no. 19, eabf9668
DOI: 10.1126/sciadv.abf9668
  • Fig. 1 Phenomena of impurity-induced RTP.

    (A) RTP spectra of 1BBI with different purification. Excitation, 365 nm; slit width, 10 nm; voltage, 700 V. a.u., arbitrary units. (B) RTP decay curve of 1BBI with different purification. (C) Structure of DMIQI and 1BBI identified by single-crystal x-ray diffraction. (D) Different luminescent performance between crude and extra-pure 1BBI under 365-nm irradiation. UV, ultraviolet. (E) RTP spectra of 1BBI mixed with various contents of DMIQI. Excitation, 365 nm; slit width, 10 nm; voltage, 650 V. (F) Changes of phosphorescence intensity (value at 550 nm) and lifetime with different molar ratios.

  • Fig. 2 Optical characteristics of trace ingredient–mediated bicomponent RTP systems.

    (A) Chemical structures of seven selected ingredients. (B) Normalized RTP spectra of trace ingredient–mediated bicomponent RTP systems. (C) RTP decay curve of trace ingredient–mediated bicomponent RTP systems. (D) Afterglow images of trace ingredient–mediated bicomponent RTP systems. The spectra and images of 2BBI/1BBI and 4BBI/1BBI were measured under 254-nm excitation and others under 365 nm.

  • Fig. 3 Crystal analysis of DMBA/1BBI solid.

    (A) XRD pattern of DMBA/1BBI before and after grinding. (B) RTP intensity change of DMBA/1BBI before (red line) and after (blue line) grinding. (C) Melting points of the DMBA/1BBI mixture compared with single components.

  • Fig. 4 Optical characteristics of trace ingredient–mediated bicomponent system using DIB matrix and corresponding mechanism.

    (A) Normalized RTP spectra of trace ingredient–mediated bicomponent system using DIB matrix at 1 mol % contents. (B) RTP intensity decay curve of trace ingredient–mediated bicomponent system using DIB matrix at 1 mol % contents. (C) Fluorescence spectra (solid line and left y axis; excitation, 254 nm; slit width, 5 nm; voltage, 400 V) and RTP spectra (dashed line and right y axis; excitation, 254 nm; slit width, 5 nm; voltage, 600 V) of 4BBI/DIB at various proportions. (D) Fluorescence decay of DIB before and after being mixed with 4BBI. (E) Electron and hole motion after photoexcitation. Upon photoexcitation, electrons were transported from HOMO to LUMO of the matrix (I). Then, electrons from HOMO of impurities were transferred to the HOMO of the excited matrix to generate the charge transfer state (II). The resulting electrons and holes diffused in different directions to form free charge carriers (III). Last, nongeminate radiative recombination of free charge carriers generated luminescence (IV). (F) Defect-induced charge recombination. The impurities worked as defects or energy traps and enhanced the charge recombination process. RISC, reverse intersystem crossing; IC, internal conversion.

  • Fig. 5 White-light emission system.

    (A) Steady-state luminescence of 1% DMQI/1BBI under 280-nm excitation. (B) Images of 1% DMQI/1BBI under daylight or 280-nm excitation. (C) CIE coordinate of 1% DMQI/1BBI luminescence.

  • Table 1 RTP emission peaks, lifetimes, and QYs of trace ingredient–mediated RTP systems.

    Two-compound systemλpmax (nm)τp (ms)QYp*
    MatrixIngredient
    1BBI2BBI4826.88.3%
    4BBI4828.074.2%
    DMBA46512214.8%
    PBA48011319.6%
    JCA4951432.6%
    DMIQI520, 5502336.0%
    DMQI5562627.6%
    DIB2BBI4924.47.3%
    4BBI4922.76.1%
    DMBA467724.1%
    PBA470846.4%
    JCA510663.7%
    DMIQI5501861.4%
    DMQI5644306.4%

    *The absolute phosphorescence QY was measured in solid state at room temperature.

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