Structural and electrical properties of polymorphic pentacene thin films

Stadlober, Barbara; Satzinger, Valentin; Maresch, H.; Somitsch, D.; Haase, A.; Pichler, Heinz; Rom, Werner; Jakopič, Georg

doi:10.1117/12.505868

Cited by 14 publications

(4 citation statements)

References 20 publications

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“…Precise control and optimization of the film quality are essential for the performance of OTFTs, as the structure and degree of ordering of the films have spectacular effects on the transport properties 9. 22–25 In fact, these properties depend strongly on the intermolecular overlap of electronic wave functions within the semiconductor layer and thus are very sensitive to the molecular packing 4. 5, 12, 13, 26–28 For this reason, it is of interest to summarize the available experimental information on the structure of bulk28–33 and thin‐film10–16, 22 forms of pentacene.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, since metastable phases may survive for very long times, thermodynamic metastability is not necessarily a cause of concern for the device user. However, metastability may represent a problem for device preparation, since it implies that the desired structure may only be obtained under nonequilibrium conditions by carefully controlling the growth kinetics 25. 46, 47…”

Section: Introductionmentioning

confidence: 99%

“…To better understand the differences among the various thin‐film forms, and to investigate the role of the substrate, we thus decided to simulate directly a number of possible pentacene monolayers on a SiO 2 . Since we start from given initial structures (either experimental or assumed), we are not trying to model nucleation and growth25, 46, 47 of the films. Our main focus is on the structural properties of the monolayers and on the energetic stability of competing forms.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Frontside versus Backside S_N2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Bento

Bickelhaupt

2008

Chemistry An Asian Journal

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We have theoretically studied the gas-phase nucleophilic substitution at group-14 atoms (S(N)2@A) in the model reactions of Cl(-)+AH(3)Cl (A=C, Si, Ge, Sn, and Pb) using relativistic density functional theory (DFT) at ZORA-OLYP/TZ2P. Firstly, we wish to explore and understand how the reaction coordinate zeta, and potential energy surfaces (PES) along zeta, vary as the center of nucleophilic attack changes from carbon to the heavier group-14 atoms. Secondly, a comparison between the more common backside reaction (S(N)2-b) and the frontside pathway (S(N)2-f) is performed. The S(N)2-b reaction is found to have a central barrier for A=C, but none for the other group-14 atoms, A=Si-Pb. Relativistic effects destabilize reactant complexes and transition species by up to 10 kcal mol(-1) (for S(N)2-f@Pb), but they do not change relative heights of barriers. We also address the nature of the transformation in the frontside S(N)2-f reactions in terms of turnstile rotation versus Berry-pseudorotation mechanism.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Frontside versus Backside S_N2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Bento

Bickelhaupt

2008

Chemistry An Asian Journal

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“…Organic semiconductors are known to exhibit a large variety of morphologies, which differ in their local molecular arrangements. For example, the morphology of pentacene can be varied from micron-sized single crystals, , via polycrystalline phases, with crystalline grains in the 10–100 nm range, − to amorphous phases. , Such variations affect the local electronic properties through variations in electronic coupling between molecular orbitals and local variations in the dielectric polarization effects. Such local features can substantially influence global properties.…”

Section: Introductionmentioning

confidence: 99%

Investigating a Combined Stochastic Nucleation and Molecular Dynamics-Based Equilibration Approach for Constructing Large-Scale Polycrystalline Films

Schellhammer

Cuniberti

Ortmann

2021

J. Chem. Theory Comput.

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The morphology of small-molecule organic semiconducting materials can vary from single crystals via polycrystalline films with varying grain sizes to amorphous structures, depending on the process conditions. This structural variety affects the electronic properties and, thus, the performance of organic electronic devices. A nucleation-equilibration approach is investigated, whose focus is on the construction of morphologies with controlled variations in the average grain size. Its computational requirements are low because nucleation is purely based on geometrical considerations, thus allowing the construction of model systems of experimentally relevant sizes. Its application is demonstrated for C 60 and pentacene by generating single-component films that vary from amorphous to crystalline structures. It is further generalized to twocomponent films and applied to C 60 : pentacene blends as well as dilute n-doped C 60 structures. When combined with electronic structure calculations in the future, the nucleation-equilibration approach can offer insights into the impact of polycrystallinity on electronic and charge-transport properties in the absence of any knowledge about the growth mechanism and for a broad set of systems.

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Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

Jones

Chattopadhyay

Geerts

et al. 2016

Adv Funct Materials

228

280

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2233wileyonlinelibrary.com to that of the bulk liquid; [ 7 ] order typically exists over a few molecular layers before rapidly decaying to bulk behavior as the distance from the wall increases. [ 8 ] Similar ordering effects can also be observed in the quasiliquids which form on the surface of many solids due to surface melting (also known as premelting): [ 9,10 ] the existence of a liquid-like layer a few molecules thick on the surface of a solid below the melting point of the bulk material. [ 11 ] The structure within this layer is also found to be different to that of the bulk isotropic liquid, [ 12 ] highlighting the ordering occurring at the interface. A converse effect, surface freezing, is also observed in some liquids (primarily n -alkanes with 16 ≤ n ≤ 50), where a solid monolayer may exist at an interface up to ≈30 °C above the bulk melting point while the rest of the compound is molten. [13][14][15] Such phase behavior is strongly dependent on molecular shape and has only been observed for chain molecules, which then form layers similar to self-assembled monolayers (SAMs) at the interface with the liquid bulk. [ 16 ] Further examples of molecular ordering at interfaces can be seen in materials which display liquid crystal (LC) phases, a phase behavior also dependent on molecular shape and generally observed for molecules with a highly anisotropic shape (e.g., rod-like, disc-like or bowl-like molecules). [ 17 ] LCs have properties of both solids and liquids and display long range order which may be orientational and/or positional; various types of LC phases (mesophases) are possible and normally exist only over a certain temperature range (i.e., they are thermotropic); a further property of LCs is that they generally reach thermodynamic equilibrium in the bulk and at interfaces as a result of their short relaxation time. Nematic (N) phases of calamitic LCs (rod-like molecules with cylindrical symmetry) have no positional order but an orientational order which can be described by a unit vector, n , known as the director, which represents the preferred molecular orientation ( Figure 1 , left). A scalar order parameter can also be defi ned which is related to the average angle the long molecular axes make to the director, n .Increased order is seen in smetic phases (Sm) which have both orientational and positional order; for example in a smetic A phase (SmA) molecules form layers (positional ordering of the molecular mass centers) which are oriented normal to the plane of the layers (orientational order), while smetic C phases (SmC) form layers where molecules are oriented with the long molecular axes tilted at an angle to the molecular layer normal However, the factors that drive such a process are not clearly understood or studied in depth. In this feature article, we review the current state of understanding concerning SIPs, giving examples of systems where SIPs have been observed, discussing their origins, and which questions remain to be answered. The role of the substrate in controlling the growth a...

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Structural and electrical properties of polymorphic pentacene thin films

Cited by 14 publications

References 20 publications

Frontside versus Backside S_N2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Frontside versus Backside S_N2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Investigating a Combined Stochastic Nucleation and Molecular Dynamics-Based Equilibration Approach for Constructing Large-Scale Polycrystalline Films

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

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Structural and electrical properties of polymorphic pentacene thin films

Cited by 14 publications

References 20 publications

Frontside versus Backside SN2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Frontside versus Backside SN2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Investigating a Combined Stochastic Nucleation and Molecular Dynamics-Based Equilibration Approach for Constructing Large-Scale Polycrystalline Films

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

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Product

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Frontside versus Backside S_N2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence

Frontside versus Backside S_N2 Substitution at Group 14 Atoms: Origin of Reaction Barriers and Reasons for Their Absence