Hybrid LbL/LB films as molecular OLEDs: An acoustic shear wave attenuation and Brewster angle microscopy study

Molecularly organized organic light-emitting diodes (OLEDs) were constructed using a combination of polyelectrolyte Layer-by-Layer (LbL) assembly and Langmuir–Blodgett (LB) deposition. The hetero-structure was based on poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene) (MEH–PPV), on poly(methacrylic acid) (PMA) and on poly(ethylenimine) (PEI). The film-forming properties of MEH–PPV were investigated at the water–air interface by recording surface pressure–area and surface potential–area isotherms. Stable MEH–PPV monolayers were transferred by means of the LB technique on solid supports. The assembling process of the LbL layers was followed by quartz crystal microbalance (QCM) measurements. The final multilayered structure was characterized by means of ellipsometric thickness determination, static contact angle and conductivity measurements. The morphology of the outer surface of the LbL/LB/LbL structure was analyzed by means of Brewster angle microscopy (BAM) studies. The optical response of the hybrid multilayer was tested measuring the electronic absorption and the emission spectra.