Thickness and annealing temperature effects on the optical properties and surface morphology of layer‐by‐layer poly(p‐phenyline vinylene)+dodecylbenzenesulfonate films

Abstract

The fabrication of controlled molecular architectures is essential for organic devices, as is the case of emission of polarized light for the information industry. In this study, we show that optimized conditions can be established to allow layer‐by‐layer (LbL) films of poly(p‐phenylene vinylene) (PPV)+dodecylbenzenesulfonate (DBS) to be obtained with anisotropic properties. Films with five layers and converted at 110 °C had a dichroic ratio δ = 2.3 and order parameter r = 34%, as indicated in optical spectroscopy and emission ellipsometry data. This anisotropy was decreased with the number of layers deposited, with δ = 1.0 for a 75‐layer LbL PPV + DBS film. The analysis with atomic force microscopy showed the formation of polymer clusters in a random growth process with the normalized height distribution being represented by a Gaussian function. In spite of this randomness in film growth, the self‐covariance function pointed to a correlation between clusters, especially for thick films. In summary, the LbL method may be exploited to obtain both anisotropic films with polarized emission and regular, nanostructured surfaces. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Substrate/semiconductor interface effects on the emission efficiency of luminescent polymers

“…about 200 C, as a thermal treatment above this temperature affects the packing of the chains substantially. Some of this characterization was already performed in our earlier paper, 18 but the data then obtained were not sufficient to determine precisely where polymer bulk properties should dominate. For example, the dichroic ratio (d) varied abruptly from 5 to 25 bilayers and the p-polarized emission varied linearly with the film thickness, and therefore no information could be obtained as to where interface effects were still important.…”

“…Table I being important up to 25 bilayers, since 50-and 75-bilayer LBL films did not display a significant change in the PPV effective conjugation degree (see Table I). Figure 1 (inset) shows a linear dependence between the absorbance at 420 nm and the number of bilayers, which means that the same amount of material was deposited in each layer, with a thickness of 3 nm per layer according to AFM measurements (not shown) 18 (see Table I). The root-mean-square (rms) roughness (r rms ) increased with the number of bilayers, from 6 to 44 nm and from 4 to 25 nm for 5 and 75 bilayers, with films thermally converted at 230 and 110 C, respectively.…”

“…PPV was converted with two conversion temperatures, namely 110 and 230 C, to verify how changes in oxidative defects could affect emission. The films studied are essentially the same as in our previous paper, 18 but we employed further characterization strategies to determine the interface effects precisely, which was not possible in the earlier study. Indeed, in addition to studying the temperature dependence of the photoluminescence (PL) spectra and obtaining the photoluminescence excitation spectra (PLE), we include calculation of multireflection on the interfaces of excited light and a physical model that demonstrates the importance of interface effects.…”

Electrochemical Deposition of P3AT Films Used as a Probe of Optical Properties in Polymeric System

“…This is due to the presence of oligomers with smaller conjugation lengths [38] and quinone chains [8,19]. In addition for EtNBF01-EtNBF04 ilms, it is possible the occurrence of polymer chains with lower molecular weight and interface substrate/polymer, polymer/polymer and polymer/ electrolyte efects [14,22]. By increasing the ilm thickness (>4 cycles), PL spectra shifted to high wavelengths (redshift), it according the rise of in residence time in the electropolymerization process in the presence of higher conjugated polymer chains and pristine structures [8,9,12].…”

“…Since the physical-chemistry properties and investigation of organic active layers, such as P3ATs thin solid ilms, can elucidate the development of new optoelectronic devices [16][17][18]. Interface efects cause signiicant quenching of excited carriers and it is commonly investigated by conventional spectroscopic techniques [15,19], such as ultraviolet-visible absorption (UV-Vis), photoluminescence (PL), photoluminescence excitation (PLE), vibrational spectroscopy (FT-IR and RAMAN) [8,12,20,21] and the morphological technique of atomic force microscopy (AFM) [22][23][24]. In the case of energy transfer processes of excited carriers, the analysis of polarization of emited light can be directly correlated with polymeric chain position parallel to the direction of the transition dipole moment [25][26][27].…”