Determination of the width of the density of states of the highest occupied molecular orbital in pentacene

Jena, Sanjoy; Ray, Debraj

doi:10.1016/j.tsf.2019.137765

Cited by 3 publications

(14 citation statements)

References 45 publications

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“…Both pentacene and NPB are hole conducting materials, with pentacene having orders of magnitude higher hole mobility compared to NPB (0.01–10 cm 2 /V·s in pentacene , and 10 –5 –10 –4 cm 2 /V·s in NPB). The highest occupied molecular orbital (HOMO) level of pentacene is −5 to −5.2 eV, , and that of NPB is around −5.4 to −5.5 eV. , Therefore, while using palladium (Pd) as the source/drain contacts (Pd has a work function of −5.1 eV), pentacene has almost no barrier for the hole injection, whereas NPB has around 0.4 eV energy barrier.…”

Section: Resultsmentioning

confidence: 99%

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Spatial Extent of Interaction between Excitons and Polarons in a Bilayer Organic Field-Effect Transistor

et al. 2021

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A major loss mechanism in high intensity organic light-emitting devices is the quenching of excitons in the presence of polarons. In this work, the interaction of excitons in N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) with holes in pentacene is studied in a pentacene/NPB bilayer organic field-effect transistor. Gate-modulated steady-state photoluminescence quenching measurements are performed. The excitons are confined in NPB and the polarons in an ultrathin layer of pentacene at the pentacene/NPB organic heterojunction. It is shown that excitons are quenched by polarons, even if they are located on different materials, provided that the exciton and polaron are separated by a length within which efficient Forster resonance energy transfer can occur. The experimental findings are supported by a steady-state three-dimensional simulation of the gate voltage-dependent exciton−polaron quenching efficiency. The Forster resonant energy transfer radius for exciton−polaron interaction at the pentacene/NPB heterojunction is estimated to be in the range of 2.3−3.0 nm.

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Section: Resultsmentioning

confidence: 99%

“…Both pentacene and NPB are hole conducting materials, with pentacene having orders of magnitude higher hole mobility compared to NPB (0.01−10 cm 2 /V•s in pentacene 22,23 and 10 −5 −10 −4 cm 2 /V•s in NPB 24 ). The highest occupied molecular orbital (HOMO) level of pentacene is −5 to −5.2 eV, 22,25 and that of NPB is around −5.4 to −5.5 eV.…”

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Spatial Extent of Interaction between Excitons and Polarons in a Bilayer Organic Field-Effect Transistor

et al. 2021

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“…In the output characteristics, V GS remains constant, and V DS is varied. The method and its advantages has been described elsewhere [42]. The method uses linear fitting of drain conductance plot to calculate charge carrier mobility at each V GS .…”

Section: Methodsmentioning

confidence: 99%

“…If the dispersion of mobility with V GS is high (for e.g. 90 • C in HR OTFTs, figure 10(b)), the system is said to be more disordered [41,42]. In case the dispersion is low (for e.g.…”

Section: Electrical Responsementioning

confidence: 99%

“…Charge carrier mobility and its charge carrier concentration-dependence along with morphology and crystallinity are used to understand the effect of depositions parameters on the performance of OTFTs. The width of the Gaussian density of states (DOS) comprising the HOMO is used to estimate the disorder in OTFTs grown under different conditions [41,42].…”

Section: Introductionmentioning

confidence: 99%

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Influence of film morphology and crystallinity on charge carrier concentration-dependent hole mobility in hexamethyldisilazane treated Pentacene bottom contact devices

Jena¹,

Rajpoot²,

Dutta³

et al. 2021

J. Phys. D: Appl. Phys.

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The effect of substrate temperature and deposition rate on the film morphology, crystallinity, and electronic properties of Pentacene transistors treated with hexamethyldisilazane (HMDS) is studied. The gate bias dependence of mobility is used to estimate the width of the density of states and thereby quantify the disorder of the highest occupied molecular orbital. A low deposition rate and the substrate held at room temperature are shown to be the optimal conditions for good mobility (0.20 cm2 V−1 s−1) and low electronic disorder (50 ± 10 meV). X-ray diffraction measurements are performed to quantify the ratio of the two crystalline phases (thin-film phase and bulk phase) present in the film. The crystalline phases, rather than grain size, plays a significant role in determining the charge carrier mobility. Film deposition with the substrate at room temperature leads to low electronic disorder as the film is composed of one crystalline phase (thin-film phase), while high substrate temperature makes the film increasingly polymorphic, leading to increased electronic disorder (up to 230 meV). A high deposition rate leads to poor morphology of Pentacene near the source/drain electrode edge, thereby leading to increased contact resistance and electronic disorder. Hence, a low growth rate at room temperature is required for HMDS treated substrates to induce good crystalline properties of the film in the channel region, which results in enhanced electronic properties of the transistors.

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A study on the effect of film crystallinity and morphology on charge carrier concentration-dependent hole mobility in pentacene thin-film transistors: advantages of high deposition rate

Jena

Ray

2020

J. Phys. D: Appl. Phys.

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The combined effect of deposition rate and substrate temperature on the film crystallinity, morphology, and electronic properties of pentacene is studied. It is shown that the channel mobility in polycrystalline pentacene thin-film transistors is relatively immune to substrate temperature, and the films offer good hole mobility when grown at a high rate. This is advantageous when high throughput with low deviation in electrical parameters over devices are required. The surface morphology is characterized by atomic force microscopy measurements and the crystallinity is studied using x-ray diffraction. The effect of growth parameters on the crystalline phases of pentacene is correlated to the charge carrier transport. It is found that the field-effect mobility is primarily affected by the crystalline phases of the film rather than the grain size. The charge carrier dependence of the hole mobility is used to parameterize the dispersion (width) in the density of states (DOS) of the highest occupied molecular orbital of the films in the transistor channel region. It is found that the presence of multiple phases in the path of the charge carrier flow increases the dispersion of the DOS.

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Determination of the width of the density of states of the highest occupied molecular orbital in pentacene

Cited by 3 publications

References 45 publications

Spatial Extent of Interaction between Excitons and Polarons in a Bilayer Organic Field-Effect Transistor

Spatial Extent of Interaction between Excitons and Polarons in a Bilayer Organic Field-Effect Transistor

Influence of film morphology and crystallinity on charge carrier concentration-dependent hole mobility in hexamethyldisilazane treated Pentacene bottom contact devices

A study on the effect of film crystallinity and morphology on charge carrier concentration-dependent hole mobility in pentacene thin-film transistors: advantages of high deposition rate

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