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UV-visible absorption (solid line) and PL spectra (open circle) of MEHT-PPV solution and PL spectrum (solid square) of PFO thin film. For a comparison, PL spectrum (open diamond) of MEH-PPV solution is also plotted in it. The inset shows chemical structures of the luminescent polymers.
(Color online) PL spectrum of PFO blended with MEHT-PPV, and EL spectra of the single-layer WPLEDs made with PFO blended with 0.5 and MEHT-PPV. For a good comparison, EL spectrum of the PFO/MEH-PPV device is also plotted in it. The inset shows the photograph of the single-layer device based on the blend of PFO and MEHT-PPV with an emission area of .
(a) Brightness-voltage characteristics and (b) EL efficiency-current density characteristics of the single-layer and bilayer WPLEDs with MEHT-PPV as EMLs and with different HTLs. The symbols in (a) show the compositions of HTLs, which are also applicable in (b). The inset of (b) shows energy levels of the polymers involved in the devices.
Cross-section SEM images of HTL/EML bilayer interfaces on the electrode. The HTL is PVK (left) and the 1:1 blend of poly-TPD and PVK (right). The EML is PFO blended with MEHT-PPV for both samples.
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