Research ArticleELECTRICAL CONDUCTORS

Long-range coupling of electron-hole pairs in spatially separated organic donor-acceptor layers

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Science Advances  26 Feb 2016:
Vol. 2, no. 2, e1501470
DOI: 10.1126/sciadv.1501470
  • Fig. 1 Photoluminescence characteristics of the exciplex system.

    (A) Chemical structures of electron-donating (D), spacer (S), and electron-accepting (A) molecules. (B) Steady-state fluorescence spectra of D:S, A:S, and D:A co-deposited films. (C and D) Steady-state fluorescence spectra of neat and doped films. The broad emission band with a peak at around 500 nm in the T2T neat film is assigned to excimer emission [that is, 1(AA)*]. (E) Room-temperature time-resolved fluorescence decay curve of a D:A film. Inset: Room-temperature time-resolved fluorescence decay curves of D:S and S:A films. (F) Steady-state fluorescence spectra of multilayer thin films [10-nm-thick D/x-nm-thick S (x = 0, 10, 30, 50, 70, 90, 120, and 150 Å)/20-nm-thick A]. Inset: Schematic illustration of a multilayer D (blue)/S/A (red) film. The excitation light (λex = 300 nm) was incident from the side of the D layer.

  • Fig. 2 Electroluminescence characteristics of the exciplex system.

    (A) Structures and energy diagram of OLEDs. Energy gaps were estimated from absorption edges of films. The anode and cathode were 100-nm-thick indium tin oxide and 5-nm-thick lithium fluoride/100-nm-thick aluminum, respectively. (B) EL spectra of devices with various spacer-layer thickness (d) at a luminance of 1000 cd/m2. (C) Room-temperature time-resolved EL decay curves for devices with d = 0, 10, 30, and 50 Å. OLEDs were exposed to a pulse voltage with a duration of 5 μs. (D) External EL quantum efficiency against luminance for devices with various d. (E) Dependence of EL spectra on applied electrical field for devices with a spacer-layer thickness of d = 90 Å.

  • Fig. 3 Resonant transfer of the exciplex energy to energy acceptor molecules.

    (A) EL spectrum of an energy transfer–type device at a luminance of 200 cd/m2. The dashed line shows the PL spectrum of a 2 wt % DBP:mCBP co-deposited film. Inset: Schematic illustration of the emission layer. (B) Time-resolved EL decay curves measured for a device with d = 50 Å at room temperature. EL was accumulated after exposure of each OLED to a pulse voltage with a duration of 5 μs. Inset: Accumulated emission spectra for total (black), prompt (red), and delayed (blue) components.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/2/e1501470/DC1

    Fig. S1. UV-vis absorption spectra.

    Fig. S2. Time-resolved PL spectra of D:A co-deposited films.

    Fig. S3. The dependence of exciton energy on distance between D and A.

    Fig. S4. Dependence of EL spectra on luminance.

    Fig. S5. Time-resolved EL spectra for a device with spacing layer thickness d = 100 Å.

    Fig. S6. External EL quantum efficiency for a device with spacing layer and for a device with a D:A co-deposited film as an emissive layer.

    Fig. S7. Performance of an OLED with an ADN spacer layer.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. UV-vis absorption spectra.
    • Fig. S2. Time-resolved PL spectra of D:A co-deposited films.
    • Fig. S3. The dependence of exciton energy on distance between D and A.
    • Fig. S4. Dependence of EL spectra on luminance.
    • Fig. S5. Time-resolved EL spectra for a device with spacing layer thickness d = 100 Å.
    • Fig. S6. External EL quantum efficiency for a device with spacing layer and for a device with a D:A co-deposited film as an emissive layer.
    • Fig. S7. Performance of an OLED with an ADN spacer layer.

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