Equilibrium theory of space charge layers in conjugated polymers I. Non-degenerate limit

Paasch, G.; Nguyen, Pham Dinh; Drechsler, S.‐L.

doi:10.1016/s0379-6779(98)00138-6

Cited by 19 publications

(15 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The only specifics is, that owing to the large band width of an inorganic semiconductor, N V is much smaller (usually about 10 19 cm À3 ) than the monomer density. However, in an organic semiconductor with polarons as charged states of polymer chains, one has again to use for N V the monomer density [24]. Considering multiple redox sites is equivalent to degeneration factors in the density.…”

Section: Limit Of Low Concentrationsmentioning

confidence: 99%

“…The Nernst equations are in the low concentration or nondegenerate approximation [20,24] c 0 c P þ equ:…”

Section: Polarons and Bipolaronsmentioning

confidence: 99%

“…The non-degenerate approximation is valid below E É 3 and up to more than 10% oxidation degree [24,25]. Such high concentrations are not achieved in space charge layers in organic devices.…”

Section: Polarons and Bipolaronsmentioning

confidence: 99%

“…[23] it has been stated that the two processes (24) and (27) are considered as parallel. Actually, the ac small signal analysis was done there separately for each process.…”

Section: Slow Processes: Ac Small-signal Analysismentioning

confidence: 99%

“…The possible rule of BPs in organic devices has been discussed rarely [24,25]. Recently, it has been suggested [23,26] that both the direct P-BP reaction and the formation of a complex consisting of a BP and two Cs could be determinative for hysteresis effects which are typically for present organic field-effect devices [11,[27][28][29][30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Transport and reactions in doped conjugated polymers: Electrochemical processes and organic devices

Paasch

2007

Journal of Electroanalytical Chemistry

View full text Add to dashboard Cite

Section: Limit Of Low Concentrationsmentioning

confidence: 99%

“…The Nernst equations are in the low concentration or nondegenerate approximation [20,24] c 0 c P þ equ:…”

Section: Polarons and Bipolaronsmentioning

confidence: 99%

Section: Polarons and Bipolaronsmentioning

confidence: 99%

“…[23] it has been stated that the two processes (24) and (27) are considered as parallel. Actually, the ac small signal analysis was done there separately for each process.…”

Section: Slow Processes: Ac Small-signal Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Transport and reactions in doped conjugated polymers: Electrochemical processes and organic devices

Paasch

2007

Journal of Electroanalytical Chemistry

View full text Add to dashboard Cite

Characteristics and mechanisms of hysteresis in polymer field‐effect transistors

Paasch¹,

Scheinert²,

Herasimovich³

et al. 2008

Physica Status Solidi (a)

View full text Add to dashboard Cite

Hysteresis effects do occur usually in polymer field‐effect devices. It has been suggested that trap recharging or mobile ions, or formation/dissociation of bipolarons (BP) in the accumulation layer can cause this effect. Here, at first a literature survey on the hysteresis in field‐effect transistors is given. Then examples of measured hysteresis in field‐effect transistors and in metal‐insulator‐semiconductor (MIS) capacitors are presented. The typical peculiarity is the dependency of the flat band voltage on the sweep direction of the gate voltage. Our recent numerical simulations on the trap recharging mechanism in MIS capacitors are continued and extended to transistors. Energetically distributed traps can lead to hysteresis. But the form of the hysteresis deviates from the observed one and extreme parameter values are needed. Thus it is more likely that trap recharging can modify a hysteresis caused by another mechanism. For discussing the bipolaron mechanism the equilibrium between polarons and doubly charged states of the polymer chains was analyzed anew. With a rate constant for the bipolaron formation determined recently by Salleo and Street relaxation times for formation/dissociation are determined. They indicate that these processes can cause the hysteresis. A further possible mechanism influencing the hysteresis is connected with complexes between polarons, bipolarons and mobile counter ions. The estimated rate constants indicate processes on the time scale of the measurements. Numerical simulations of these processes as well as of the role of mobile ions and their reactions are required for a full description of the hysteresis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

show abstract

Ambipolar charge carrier transport in organic semiconductor blends of phthalocyanine and fullerene

Bronner

Opitz²,

Brütting

2008

Physica Status Solidi (a)

View full text Add to dashboard Cite

Ambipolar charge carrier transport is realised in organic field‐effect transistors using mixtures of p‐conductive copper‐phthalocyanine and n‐conductive buckminster fullerene as active layer. These blends are model systems for ambipolar transport with adjustable field‐effect mobilities for electrons and holes by variation of the mixing ratio. Thereby balanced mobilities for both charge‐carrier types are possible. In this paper we discuss the variation of mobility, threshold voltage and electronic energy levels with the mixing ratio. The charge carrier mobilities are strongly reduced upon dilution of the respective conducting phase by the other species. This shows that transport of each carrier species occurs by percolation through the respective phase in the blend. A strong correlation between contact resistance and mobility indicates that carrier injection is diffusion limited. A charge redistribution in the copper‐phthalocyanine causes a hole accumulation at the organic/organic interface and affects thereby the threshold voltage for holes. By analysing the electronic structure using photoelectron spectroscopy no charge transfer was found in the ground state. The common work function of these blends changes linearly between the work functions of the neat materials. Thus a constant ionisation potential for the highest occupied molecular orbitals of the two materials is obtained. Furthermore we have fabricated ambipolar inverters using mixed organic semiconductor layers and compare their behaviour to complementary inverters consisting of discrete p‐ and n‐channel transistors. The experimental findings and concomitant simulations demonstrate the need for balanced elec‐ tron and hole mobilities in order to achieve symmetric inverter characteristics. However, they also reveal the superior performance of true complementary logic inverters towards their ambipolar pendants. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

show abstract

Equilibrium theory of space charge layers in conjugated polymers I. Non-degenerate limit

Cited by 19 publications

References 19 publications

Transport and reactions in doped conjugated polymers: Electrochemical processes and organic devices

Transport and reactions in doped conjugated polymers: Electrochemical processes and organic devices

Characteristics and mechanisms of hysteresis in polymer field‐effect transistors

Ambipolar charge carrier transport in organic semiconductor blends of phthalocyanine and fullerene

Contact Info

Product

Resources

About