Real-time X-ray diffraction measurements of structural dynamics and polymorphism in diindenoperylene growth

Kowarik, Stefan; Gerlach, Alexander; Sellner, Stefan; Cavalcanti, Leide P.; Konovalov, Oleg; Schreiber, Frank

doi:10.1007/s00339-008-5012-2

Cited by 42 publications

(64 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The SIP of 8 , as reported by Durr et al, is identical in structure to the high temperature β ‐phase . It must be noted here that the substrate acts to stabilize the β ‐phase structure ≈200 K below the temperature where a phase transition to a low temperature phase is observed in the bulk . In‐situ GIXD measurements studying the film growth of 8 on different substrates showed that the first monolayer consisted of molecules in a more upright orientation, similar to the monolayer structure of 1 .…”

Section: Experimentally Observed Sipssupporting

confidence: 80%

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

Jones

Chattopadhyay

Geerts

et al. 2016

Adv Funct Materials

231

280

View full text Add to dashboard Cite

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...

show abstract

Section: Experimentally Observed Sipssupporting

confidence: 80%

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

Jones

Chattopadhyay

Geerts

et al. 2016

Adv Funct Materials

231

280

View full text Add to dashboard Cite

show abstract

“…The factor 1.2 is introduced to correct for the differences in the unit cell volumes of PFP 42 and DIP. 58 As it can be seen in Fig. 3 Table I.…”

Section: A Post Growth Xrr-measurementsmentioning

confidence: 84%

Structure formation in perfluoropentacene:diindenoperylene blends and its impact on transient effects in the optical properties studied in real-time during growth

Broch

Gerlach

Lorch

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

We discuss the result of the competing effects of favourable intermolecular interactions and steric incompatibilities due to the size mismatch of perfluoropentacene (PFP) and diindenoperylene (DIP) on the structure formation and associated optical properties in mixed films. Using real-time grazing incidence X-ray diffraction we investigate the size of coherently scattering islands l(s) as a function of film thickness and mixing ratio. We find that for PFP:DIP 1:2 blends l(s) is by a factor of ~4 smaller than in pure DIP films, while l(s) of the PFP:DIP 2:1 blends is not significantly reduced compared with pure PFP. Yet, we observe an increase in l(s) with film thickness for all of the samples, independent on the mixing ratio. In parallel with the structural characterization we investigate the evolution of the absorption spectra in the visible spectral range and its dependence on l(s) in situ during film growth using differential reflectance spectroscopy. We observe a surprisingly strong effect of changes in the structural order on the shape of ε(2, xy)(E), evident by a pronounced evolution of characteristic peaks in the thickness range from 1.6 nm to 9.6 nm. The combined results of the real-time experiments allow to identify the thickness dependent crystal grain size as the origin of the observed transient effects in the absorption spectra.

show abstract

“…However, it is not easy to conclude from a rougher surface a higher l s directly, since the differences in r are relatively low compared to the differences observed for l s . Interestingly, no indications of lying-down DIP molecules or the low-temperature bulk crystal phase are observed at T sub ¼ 243 K, as is the case for pure DIP films at 233 K. 16 It is usually the case that either a high deposition rate or a low T sub should have a similar effect on the phase separation. At T sub ¼ 373 K, the influence of decreasing r dep by a factor of ten on D cohk of DIP is of the same order as increasing T sub from 303 K to 373 K. Nevertheless, decreasing the deposition rate at low substrate temperatures has a significantly smaller influence on l s than increasing T sub .…”

mentioning

confidence: 99%

“…11 DIP itself has a high exciton diffusion length, 12 exhibits ambipolar transport properties, 13 and its structural and morphological properties have been extensively studied. [14][15][16][17][18] C 60 is a commonly used acceptor material in OPV cells. [19][20][21] The two materials together form a prototypical system of phase-separating mixtures; this offers the opportunity for a detailed understanding of the fundamental aspects of such material pairs, in general.…”

mentioning

confidence: 99%

Controlling length-scales of the phase separation to optimize organic semiconductor blends

Lorch

Frank

Banerjee

et al. 2015

Applied Physics Letters

View full text Add to dashboard Cite

The length-scale of phase separation in organic semiconductor donor-acceptor mixtures, while being crucially important for applications, is a non-trivial parameter to control in non-equilibrium thin film growth. We present a comprehensive study of all the important parameters that can be used to tailor the length-scale of phase separation in organic semiconductor mixtures. We employed different substrate temperatures, different growth rates, time-dependent deposition rates, and surface functionalization layers. We found not only that the substrate temperature is most prominent in influencing the length-scale of phase separation in the studied parameter range, but also that other routes can be used to tailor this length-scale. V

show abstract

Real-time X-ray diffraction measurements of structural dynamics and polymorphism in diindenoperylene growth

Cited by 42 publications

References 30 publications

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

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

Structure formation in perfluoropentacene:diindenoperylene blends and its impact on transient effects in the optical properties studied in real-time during growth

Controlling length-scales of the phase separation to optimize organic semiconductor blends

Contact Info

Product

Resources

About