Band bending in conjugated polymer films: role of morphology and implications for bulk charge transport characteristics

Wenderott, J. K.; Dong, Ban Xuan; Green, Peter F.

doi:10.1039/c7tc02302b

Cited by 18 publications

(17 citation statements)

References 31 publications

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“…These flat bands they attributed to the high purity of the used TPD. Band bending for nominally pristine organic semiconductors has also been observed, when studying various interfaces with conjugated polymers [160][161][162][163][164][165] and when separating the metal from the organic semiconductor using an insulating alkalihalide layer. [166] In such cases, this is typically explained by the filling of electronic states in molecules at some distance from the interface.…”

Section: Organic Monolayers Versus Multilayers and Doped Filmsmentioning

confidence: 90%

The Impact of Dipolar Layers on the Electronic Properties of Organic/Inorganic Hybrid Interfaces

Zojer

Taucher

Hofmann

2019

Adv Materials Inter

138

168

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The presence of dipolar layers determines the functionality of most technologically relevant interfaces. The present contribution reviews how periodic dipole assemblies modify the properties of such interfaces through so‐called collective electrostatic effects. They impact the ionization energies and electron affinities of thin films, change the work function of metallic and semiconducting substrates, and determine the alignment of electronic states at interfaces. Dipolar layers originate either from the assembly of polar molecules or they arise from interfacial charge rearrangements triggered by the deposition of an adsorbate layer. Such charge rearrangements result from the omnipresent Pauli pushback caused by exchange interaction, from covalent bonds, or from charge transfer following the deposition of particularly electron rich (donors) or electron poor molecules (acceptors). A peculiarity of charge‐transfer interfaces is that they enter the realm of Fermi‐level pinning, where the sample work function becomes independent of the substrate and is solely determined by the electronic properties of the adsorbate. Beyond changing work functions and injection barriers, the presence of polar layers also modifies various other physical observables, like core‐level binding energies or tunneling currents in monolayer junctions. All these aspects suggest that polar layers can also be exploited for electrostatically designing the electronic properties of materials.

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Section: Organic Monolayers Versus Multilayers and Doped Filmsmentioning

confidence: 90%

The Impact of Dipolar Layers on the Electronic Properties of Organic/Inorganic Hybrid Interfaces

Zojer

Taucher

Hofmann

2019

Adv Materials Inter

138

168

View full text Add to dashboard Cite

show abstract

“…It has been shown that for conductive organic semiconductors, only the free charge carriers responsible for effective charge carrier mobility actually contribute to the formation of space charge layers, which results in band bending at an interface. 59 For such polymers, it has also been shown that band bending on the surface actually depends on the film thickness. Thus, at low concentrations of mobile charge carriers, which is considered the default situation in the majority of polymer photocatalysts, the formation of a space charge layer with significant extension is questionable.…”

Section: <Figure 2>mentioning

confidence: 99%

Polymer photocatalysts for solar-to-chemical energy conversion

et al. 2020

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Solar-to-chemical energy conversion for the generation of high energy chemicals is one of the most viable, non-intermittent solutions to the present-day lookout for sustainable energy resources. Recently, organic polymeric photocatalysts have garnered significant attention in this field of research, which has long been dominated by inorganic semiconductors. Revisiting the lessons learnt from the latter, we reevaluate the fundamental concepts of photocatalysis in the context of the different classes of polymeric photocatalysts known to date, ranging from carbon nitrides and conjugated polymers, to covalent triazine frameworks and covalent organic frameworks. We then analyze the photophysical and physicochemical concepts that govern the photocatalytic performance of these materials, and thereby derive pertinent design principles and possible future research directions in this emerging field of "soft photocatalysis".

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“…MAPLE has successfully been used to grow thin conjugated polymer films for various organic electronic applications . Our prior research has begun to elucidate fundamental connections between crystallization, morphology, electronic structure, and carrier transport in MAPLE‐deposited conjugated polymer films . An important, yet poorly understood problem is understanding the role of molecular weight on the structure and physical properties of conjugated polymers deposited by the MAPLE technique.…”

Section: Introductionmentioning

confidence: 99%

Molecular weight dependent structure and charge transport in MAPLE‐deposited poly(3‐hexylthiophene) thin films

Dong

Smith

Strzalka

et al. 2018

J Polym Sci B Polym Phys

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In this work, poly(3-hexylthiophene) (P3HT) films prepared using the matrix-assisted pulsed laser evaporation (MAPLE) technique are shown to possess morphological structures that are dependent on molecular weight (MW). Specifically, the structures of low MW samples of MAPLE-deposited film are composed of crystallites/aggregates embedded within highly disordered environments, whereas those of high MW samples are composed of aggregated domains connected by long polymer chains. Additionally, the crystallite size along the side-chain (100) direction decreases, whereas the conjugation length increases with increasing molecular weight. This is qualitatively similar to the structure of spin-cast films, though the MAPLE-deposited films are more disordered. In-plane carrier mobilities in the MAPLE-deposited samples increase with MW, consistent with the notion that longer chains bridge adjacent aggregated domains thereby facilitating more effective charge transport. The carrier mobilities in the MAPLEdeposited simples are consistently lower than those in the solvent-cast samples for all molecular weights, consistent with the shorter conjugation length in samples prepared by this deposition technique.Polymer synthesis procedure, details of Williamson-Hall analysis, Spano and Gierschner analysis, effect of benzyl alcohol on absorption spectra of P3HT solution, effect of regioregularity and PDI of P3HT on absorption spectra of P3HT thin films, and FIGURE 6 In-plane mobility of spin-cast and MAPLE-deposited samples on OTS-treated SiO 2 substrate as a function of MW. [Color figure can be viewed at wileyonlinelibrary.com]

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Band bending in conjugated polymer films: role of morphology and implications for bulk charge transport characteristics

Abstract: The band bending effect depends on the morphology of the conjugated polymer as studied by Kelvin probe force microscopy.

Cited by 18 publications

References 31 publications

The Impact of Dipolar Layers on the Electronic Properties of Organic/Inorganic Hybrid Interfaces

The Impact of Dipolar Layers on the Electronic Properties of Organic/Inorganic Hybrid Interfaces

Polymer photocatalysts for solar-to-chemical energy conversion

Molecular weight dependent structure and charge transport in MAPLE‐deposited poly(3‐hexylthiophene) thin films

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