The control of thin film morphology by the interplay of dewetting, phase separation and microphase separation

Müller‐Buschbaum, Peter; Bauer, E.; Wunnicke, Odo; Stamm, Manfred

doi:10.1088/0953-8984/17/9/006

Cited by 85 publications

(91 citation statements)

References 123 publications

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“…These morphologies strikingly resemble patterns often found in phase-separated block copolymers and polymer blend films. [57][58][59] AFM phase imaging can provide high contrast due to variations in local attractive forces and stiffness and can therefore be used as tool to discriminate between areas covered by different chemical compounds in blended films. [60][61][62] The phase image in Fig.…”

Section: Morphologymentioning

confidence: 99%

Structural and electronic properties of pentacene-fullerene heterojunctions

Salzmann

Duhm

Opitz

et al. 2008

Journal of Applied Physics

102

104

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In this study the performance differences of layered and bulk-heterojunction based organic solar cells composed of the prototypical p-and n-type organic semiconductors pentacene ͑PEN͒ and fullerene ͑C60͒ are correlated with the physical properties of the heterostructures. The electronic structure of layered and codeposited thin PEN and C60 films on the conducting polymer substrate poly͑ethylenedioxythiophene͒:poly͑styrenesulfonate͒ ͑PEDOT:PSS͒ was investigated with ultraviolet photoelectron spectroscopy. Layered structures of C60 on PEN precovered PEDOT:PSS exhibited an offset of the highest occupied molecular orbital ͑HOMO͒ levels of 1.45 eV. In contrast, codeposited films of PEN and C60 showed a reduced HOMO-level offset of 0.85 eV, which increased to 1.45 eV by precoverage of the substrate with a thin PEN layer. In this case, the PEN-HOMO level was Fermi-level pinned at 0.35 eV binding energy and charge transfer between PEN and PEDOT:PSS decreased the vacuum level by 0.75 eV. In addition, the morphology and crystal structure of the respective systems have been investigated by atomic force microscopy ͑AFM͒, x-ray diffraction ͑XRD͒ and Fourier-transform infrared spectroscopy, which indicated pronounced phase separation of PEN and C60 in the codeposited films. XRD revealed crystalline growth of PEN in all investigated cases forming crystallites that exceeded the nominal film thickness by an order of magnitude, whereas C60 was crystalline only if grown on the PEN precovered substrates. AFM investigations allowed to correlate morphology and structure revealing micro-and nanophase separation between PEN and C60.

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Section: Morphologymentioning

confidence: 99%

Structural and electronic properties of pentacene-fullerene heterojunctions

Salzmann

Duhm

Opitz

et al. 2008

Journal of Applied Physics

102

104

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“…2͑a͔͒. 20 The wiping process yields a symmetry breaking and induces a preferred orientation of the resulting structures in wiping direction.…”

mentioning

confidence: 99%

Route to create large-area ordered polymeric nanochannel arrays

Müller‐Buschbaum

Bauer

Maurer

et al. 2006

Applied Physics Letters

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Depositing polymdimethylsiloxane ͑PDMS͒ from an isopropanol solution onto a glass slide surface by wiping with a fuzz-free wipe results in highly ordered structures. Dewetting of the highly diluted PDMS solution and evaporation of the solvent yields nanostructures. The structure is well characterized as polymer nanochannels, separated by a mean distance of 166 nm. The mean height of the shallow channels is 3 nm only. The proof of having aligned structures on very large surface areas with a well defined orientation is performed with a very high resolution grazing incidence small angle x-ray scattering setup.

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“…Here, we explore the possibility to create submicron phase separated structures via dewetting of thin molecular blend films [7][8][9][10] . For systems that initially separate into bilayers, effective molecular interactions between surfaces and interfaces can play a distinct role upon solvent evaporation and destabilize the thinning film.…”

Section: Introductionmentioning

confidence: 99%

Enlarged bilayer interfaces from liquid-liquid dewetting for photovoltaic applications

et al. 2008

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The details of the arrangement of mixtures of semiconducting materials in thin-films have a major influence on the performance of organic heterojunction solar cells. Here, we exploit the phenomenon of spinodal dewetting during spin coating of blends of PCBM and a cyanine dye for the design of phase separated morphologies with increased interfacial area. AFM snapshots of as-prepared films and after selective dissolution suggest that the solution separates into transient bilayers, which destabilize due to long-range intermolecular interactions. We propose that film destabilization is effectively driven by electrostatic forces that build up due to mobile ions that cross the junction and dissolve partially in PCBM. The resulting morphology type is mainly dependent on the ratio between the layer thicknesses, whereas the dominant wavelengths formed are determined by the absolute film thickness. Solar cells were fabricated from films with known structure and a power conversion efficiency of η = 0.29 % was measured for a vertically segregated film consisting of a cyanine layer covering the anode and an upper phase composed of dewetted PCBM domains. We explain the merits of this structure in contrast to a lateral separated blend morphology where the efficiency was 3 times smaller.

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The control of thin film morphology by the interplay of dewetting, phase separation and microphase separation

Cited by 85 publications

References 123 publications

Structural and electronic properties of pentacene-fullerene heterojunctions

Structural and electronic properties of pentacene-fullerene heterojunctions

Route to create large-area ordered polymeric nanochannel arrays

Enlarged bilayer interfaces from liquid-liquid dewetting for photovoltaic applications

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