Local Charge Trapping in Conjugated Polymers Resolved by Scanning Kelvin Probe Microscopy

Hallam, Toby; Lee, MiJung; Zhao, Ni; Nandhakumar, Iris; Kemerink, Martijn; Heeney, Martin; McCulloch, Iain; Sirringhaus, Henning

doi:10.1103/physrevlett.103.256803

Cited by 66 publications

(67 citation statements)

References 18 publications

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“…[11][12][13][14] Proximal probe techniques, such as scanning Kelvin probe microscopy (SKPM), allow us to fully explore the structure-property relationships in working OTFT structures. [14][15][16][17][18][19][20][21][22][23][24][25] SKPM provides the ability to monitor changes in charge transport phenomena in both space and time, a capability not afforded by traditional electrical performance measurements a Author to whom correspondence should be addressed. Electronic mail: lucile.teague@srnl.doe.gov alone.…”

mentioning

confidence: 99%

Influence of film structure and light on charge trapping and dissipation dynamics in spun-cast organic thin-film transistors measured by scanning Kelvin probe microscopy

Teague

Loth

Anthony

2012

Applied Physics Letters

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Herein, time-dependent scanning Kelvin probe microscopy of solution processed organic thin film transistors (OTFTs) reveals a correlation between film microstructure and OTFT device performance with the location of trapped charge within the device channel. The accumulation of the observed trapped charge is concurrent with the decrease in ISD during operation (VG = −40 V, VSD = −10 V). We discuss the charge trapping and dissipation dynamics as they relate to the film structure and show that application of light quickly dissipates the observed trapped charge.

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confidence: 99%

Influence of film structure and light on charge trapping and dissipation dynamics in spun-cast organic thin-film transistors measured by scanning Kelvin probe microscopy

Teague

Loth

Anthony

2012

Applied Physics Letters

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“…The shape of the potential profile has been experimentally observed in the operating OFET by using scanning Kelvin probe microscopy (SKPM), giving linear and superlinear distributions corresponding to the linear and the saturation regions of FET output characteristics, respectively. 18 The potential profile also gives detailed information of charge transport, such as contact resistance, [18][19][20][21] charge trapping at grain boundaries, [20][21][22] as well as charge concentration dependence of the mobility. [23][24][25] However, SKPM provides no spectroscopic information of charge carriers.…”

Section: Introductionmentioning

confidence: 99%

Electron spin resonance observation of charge carrier concentration in organic field-effect transistors during device operation

et al. 2013

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Charge carrier concentration in operating organic field-effect transistors (OFETs) reflects the electric potential within the channel, acting as a key quantity to clarify the operation mechanism of the device. Here, we demonstrate a direct determination of charge carrier concentration in the operating devices of pentacene and poly(3-hexylthiophene) (P3HT) by field-induced electron spin resonance (FI-ESR) spectroscopy. This method sensitively detects polarons induced by applying gate voltage, giving a clear FI-ESR signal around g = 2.003 in both devices. Upon applying drain-source voltage, carrier concentration decreases monotonically in the FET linear region, reaching about 70% of the initial value at the pinch-off point, and stayed constant in the saturation region. The observed results are reproduced well from the theoretical potential profile based on the gradual channel model. In particular, the carrier concentration at the pinch-off point is calculated to be β/(β + 1) of the initial value, where β is the power exponent in the gate voltage (V gs ) dependence of the mobility (μ), expressed as μ ∝ V β−2 gs , providing detailed information of charge transport. The present devices show β = 2.6 for the pentacene and β = 2.3 for the P3HT cases, consistent with those determined by transfer characteristics. The gate voltage dependence of the mobility, originating from the charge trapping at the device interface, is confirmed microscopically by the motional narrowing of the FI-ESR spectra.

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“…Scanning Kelvin probe microscopes are being used to measure the variation of the potential [1][2][3] and optical probes are being used to measure the distribution and dynamics of charge in the channel. [4][5][6][7][8][9][10] In particular, dynamic measurements 6,7,10 are going beyond the usual, "lumped-impedance" approximation of a field-effect transistor (FET).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of charge flow in the channel of a thin-film field-effect transistor

Bittle

Brill

Straley

2012

Journal of Applied Physics

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The local conductivity in the channel of a thin-film field-effect transistor is proportional to the charge density induced by the local gate voltage. We show how this determines the frequency-and position-dependence of the charge induced in the channel for the case of "zero applied current": zero drain-source voltage with charge induced by a square-wave voltage applied to the gate, assuming constant mobility and negligible contact impedances. An approximate expression for the frequency dependence of the induced charge in the center of the channel can be conveniently used to determine the charge mobility. Fits of electro-optic measurements of the induced charge in organic transistors are used as examples.2

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Local Charge Trapping in Conjugated Polymers Resolved by Scanning Kelvin Probe Microscopy

Cited by 66 publications

References 18 publications

Influence of film structure and light on charge trapping and dissipation dynamics in spun-cast organic thin-film transistors measured by scanning Kelvin probe microscopy

Influence of film structure and light on charge trapping and dissipation dynamics in spun-cast organic thin-film transistors measured by scanning Kelvin probe microscopy

Electron spin resonance observation of charge carrier concentration in organic field-effect transistors during device operation

Dynamics of charge flow in the channel of a thin-film field-effect transistor

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