Mapping of Trap Densities and Hotspots in Pentacene Thin‐Film Transistors by Frequency‐Resolved Scanning Photoresponse Microscopy

Westermeier, Christian; Fiebig, Matthias; Nickel, Bert

doi:10.1002/adma.201300958

Cited by 27 publications

(21 citation statements)

References 42 publications

(33 reference statements)

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“…The shift towards more positive values is instead associated with the accumulation/entrapping of photogenerated electrons [23]. These results of and under light are in agreement with those of other pentacene-based devices reported in literature [21], [22].…”

Section: Ofet Characterization At Room Temperaturesupporting

confidence: 91%

“…When the total increment of (the photocurrent) is a function of two components: the current due to the photogenerated holes (direct photocurrent) and the current associated with the shift (photovoltaic current) towards more positive values. The latter one is specifically due to the accumulation/entrapping of photogenerated electrons [23]. A signif- Fig.…”

Section: Ofet Characterization At Room Temperaturementioning

confidence: 99%

See 1 more Smart Citation

Photosensing Properties of Pentacene OFETs Based on a Novel PMMA Copolymer Gate Dielectric

Loffredo

Grimaldi

Miscioscia

et al. 2015

J. Display Technol.

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in the present work, bottom-gate top-contact organic field effect transistors (OFETs) were fabricated by evaporating a pentacene semiconductor film on top of a new insulating poly(methyl methacrylate) (PMMA) copolymer containing acrylate units. The PMMA copolymer was synthesized in order to combine the well-known insulating properties of PMMA with the possibility to be efficiently photocured enabling photopatterning-based organic circuitry integration processes. The properties of the pentacene layer deposited on ITO/PMMA copolymer stack were studied through morphological and structural analyses. Device photoresponses and photoexcitated transients were investigated and compared to reference devices based on standard PMMA gate dielectric

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Section: Ofet Characterization At Room Temperaturesupporting

confidence: 91%

Section: Ofet Characterization At Room Temperaturementioning

confidence: 99%

Photosensing Properties of Pentacene OFETs Based on a Novel PMMA Copolymer Gate Dielectric

Loffredo

Grimaldi

Miscioscia

et al. 2015

J. Display Technol.

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show abstract

“…To maximize its mobility, the most crucial parameters for pentacene quality have been identified to be the substrate and its temperature during deposition1567. On the one hand, substrate temperatures well above 50 °C result in larger grains of the film structure with characteristic lengths of microns8. On the other hand, deposition temperature also controls the abundance of several crystallographic phases, such as thin-film phase (TFP) and bulk phase (BP) pentacene569.…”

mentioning

confidence: 99%

Sub-micron phase coexistence in small-molecule organic thin films revealed by infrared nano-imaging

Westermeier

Cernescu

Amarie³

et al. 2014

Nat Commun

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100

101

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Controlling the domain size and degree of crystallization in organic films is highly important for electronic applications such as organic photovoltaics, but suitable nanoscale mapping is very difficult. Here we apply infrared-spectroscopic nano-imaging to directly determine the local crystallinity of organic thin films with 20-nm resolution. We find that state-of-the-art pentacene films (grown on SiO2 at elevated temperature) are structurally not homogeneous but exhibit two interpenetrating phases at sub-micrometre scale, documented by a shifted vibrational resonance. We observe bulk-phase nucleation of distinct ellipsoidal shape within the dominant pentacene thin-film phase and also further growth during storage. A faint topographical contrast as well as X-ray analysis corroborates our interpretation. As bulk-phase nucleation obstructs carrier percolation paths within the thin-film phase, hitherto uncontrolled structural inhomogeneity might have caused conflicting reports about pentacene carrier mobility. Infrared-spectroscopic nano-imaging of nanoscale polymorphism should have many applications ranging from organic nanocomposites to geologic minerals.

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“…Small grain domains are usually undesirable: Grain boundaries with low‐order regions contain many morphological defects, which in turn are linked to the creation of charge carrier traps. However, carrier mobilities and threshold voltages in organic thin‐film transistor devices are determined by charge traps in the channel region, most of which are located not at the grain boundaries of the organic semiconductor, but instead at the organic/insulating‐layer interface . This argument may explain why in some cases organic thin‐film transistors with smaller grain sizes show higher mobilities than counterparts with larger grain sizes: It is the structural order and molecular orientation within the active channel at the semiconductor‐dielectric interface that is a key .…”

Section: Resultsmentioning

confidence: 99%

Surface‐directed molecular assembly of pentacene on aromatic organophosphonate self‐assembled monolayers explored by polarized Raman spectroscopy

Yazji

Westermeier

Weinbrenner

et al. 2016

J. Raman Spectrosc.

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Organophosphonate self-assembled monolayers (SAMPs) fabricated on SiO2 surfaces can influence crystallization of vapor-deposited pentacene and thus can affect device performance of pentacene-based organic thin film transistors. Polarized Raman spectroscopy is demonstrated to be an effective technique to determine the degree of anisotropy in pentacene thin films deposited on three structurally different, aromatic SAMPs grown on silicon oxide dielectrics. Vibrational characterization of pentacene molecules in these films reveals that the molecular orientation of adjacent crystalline grains is strongly correlated on the SAMP-modified dielectric surface, which results in enhanced interconnectivity between the crystallite domains, well beyond the size of a single grain. It is found that vibrational coupling interactions, relaxation energies, and grain size boundaries in pentacene thin films vary with the choice of SAMP. This information clearly shows that molecular assembly of pentacene thin films can be modulated by controlling the SAMP-modified dielectric surface, with potentially beneficial effects on the optimization of electron transfer rate

show abstract

Mapping of Trap Densities and Hotspots in Pentacene Thin‐Film Transistors by Frequency‐Resolved Scanning Photoresponse Microscopy

Cited by 27 publications

References 42 publications

Photosensing Properties of Pentacene OFETs Based on a Novel PMMA Copolymer Gate Dielectric

Photosensing Properties of Pentacene OFETs Based on a Novel PMMA Copolymer Gate Dielectric

Sub-micron phase coexistence in small-molecule organic thin films revealed by infrared nano-imaging

Surface‐directed molecular assembly of pentacene on aromatic organophosphonate self‐assembled monolayers explored by polarized Raman spectroscopy

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