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(Color online) Graph of normalized EL spectra from PVK device with 1% np loading (◻). Normalized EL from control PVK device (Δ) and PL from 1.0% np in (엯) show the separate contributions to the EL emission of the hybrid device. All films were thick and the EL measurements were taken while operating the devices at . The PL measurement was taken while exposing the nps to a light source. The PVK peak at was characteristic of intrachain excimer emission from radiative recombination across overlapping carbazole groups (Refs. 22 and 23).
(a) Band diagram showing respective work functions, conduction, and valance band energies for the different materials used in the device. np values were calculated based on their light emission. (b) The device layout.
EL spectra from two PVK (1.0% ) devices of different thicknesses operated at the specified current densities. The thick device emission with (a) current density and (b) normalized. The thick device emission with (c) current density and (d) normalized. The normalized spectra reveal a nonscalar shift to a more np dominant emission when operating the devices at high current density.
Current density-voltage characteristics for PVK devices with np mass loadings of 0.1% (엯), 0.5% (◇), 1.0% (+), and 0.0% (◻). (a) The devices follow two distinct operating regimes independent of the np loading, classic SCLC behavior under , and SCLC with an exponential trap distribution above . However, as shown in (b) the nps indirectly affect the carrier transport by reducing the device drive voltage.
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