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PL spectra of 6% [Eu1 (a) and Eu2 (b)]-doped (20%PC:74%TPD) 100 nm (Eu1)- and 120-nm-(Eu2)-thick films excited with light of wavelength 350 nm and intensity . EL spectra of Eu1 and Eu2 emitter-based LEDs: or or (c). The EL spectra were taken at . The molecular structures of Eu complexes used are indicated in the figure.
(a) The external QE vs applied field, , characteristics of the 6% Eu-BrBM (Eu1) and 6% Eu-BDBBM (Eu2)-doped (20%PC:74%TPD) emitter devices as described in Fig. 3. The data for (, , 10-phenathroline) from Ref. 6 are given for comparison (uptriangles). The lines are the predictions of theory: Onsager 1934 model fit according to Eq. (2) with and (solid line); Onsager 1938 model fit for the pairs with the initial separation efficiency and the initial separation distance (dashed line); annihilation model fit according to Eq. (1) with (dotted line); and quenching model fit obtained by introducing in place of the in Eq. (1) an -dependent with a parameter (dash-dotted lines, upper- Eu1, lower- Eu2). (b) The corresponding current density plots of EL QE. Solid lines are model fits according to Eq (1) with (Eu1), (Eu2), and ( corresponds to in Refs. 6,9).
vs representation of the current -field dependence given in the inset for the two LED structures described in the upper inset. The right-hand scale, , represents calculated from the expression for the hole SCLC with .
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