charge transport in organic semiconductors and organic field effect transistors
DESCRIPTION
Andrej Golubkov. Charge transport in organic semiconductors and organic field effect transistors. IF – Seminar, Graz, 5.11.2007. Egbert Zojer Peter Pacher Harald Etschmaier. Co-Workers. Part I: Charge transport models Comparison to inorganic semiconductors Drude model - PowerPoint PPT PresentationTRANSCRIPT
Charge transport in organic
semiconductors and
organic field effect transistors
Andrej Golubkov
IF – Seminar, Graz, 5.11.2007
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20052
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Co-Workers
Egbert Zojer
Peter Pacher
Harald Etschmaier
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20053
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Outline
Part I: Charge transport models– Comparison to inorganic semiconductors
– Drude model
– Hopping transport models
Part II: Building and analyzing FETs– Building process
– temperature dependend Measurements
Part III: Parameter extraction and first results– Parameter extraction
– Mobility vs. temperature
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20054
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Charge carrier transport models.
Part I:
overview based on reviews from
Gilles Horowitz
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20055
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Comparison
(Molecular) Crystal
Covalent Metallic
Gilles Horowitz
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20056
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Conjugated organic materials
sp2 hybridization of carbon
3 σ bonds from (2s, 2px, 2p
y)
1 π bond from 2pz
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20057
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Simple band transport: Drude model free moving carriers, acceleration by external field
scattering at phonons, impurieties
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20058
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Temperature dependence of vth
Temperature dependence of scattering process:
mean free path between
phonons, charged impurities
Simple band transport: Drude model
W. Warta
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.20059
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Polaron transport
Polarization by one single charge
dressed (by π- electros) charge
residence time
el. polarization time
bandwidth
bandgap
Gilles Horowitz
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200510
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Polaron transport
Gilles Horowitz
Silinish E.A, Capek V.
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200511
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Polaron transport
Silinish E.A, Capek V.
Eg
Charge modulated spectroscopy
Peter J. Brown
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200512
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Hopping (polaron) Transport
useful for disordered materials (polymers)
Bässler's model– transport by hopping between localized states
– (Polarisation) Energy of the states fluctuates
– DOS is described by gausian distribution of variance σ– charge transport: random walk
energy difference
intersite distance
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200513
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Hopping (polaron) Transport
Perculation theory by Vissenberg & Matters– Variable range hopping among exponential DOS
– Conduction through 'resistor network': infinite cluster with the
highest conductivity is relevant– Gate voltage (charge density) dependence
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200514
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Hopping (polaron) Transport
Pentacene
300 K 180 K 117 K
A. R. Brown
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200515
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Multiple trapping & thermal release
Assumptions– carriers arriving at trap -> capture
– release is thermaly activated
– 2 sorts of carriers
Gilles Horowitz
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200516
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Multiple trapping & thermal release
Gate Voltage (charge carrier density) dependence– Upon aplied Vg a potential Vs develops at insulator-semiconductor
interface
– shift of EF towards E
C
– trapped carrier release becomes easier
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200517
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Multiple trapping & thermal release
Gate Voltage (charge carrier density) dependence
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200518
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Multiple trapping & thermal release
Alternative approach– effective mobility vs. effective charge density
– Hall-effect measurements
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200519
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Multiple trapping & thermal release
Hall-effect results on rubrene single crystal
Menard et al
Podzorov, Menard, Rogers, Gershenson
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200520
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Summary Drude
Bässler
Vissenberg Matters
MTR
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200521
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Device fabrication
and
measurement setups
Part II:
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200522
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
OTFT, Fabrication and measurements
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200523
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200524
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200525
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200526
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200527
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200528
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200529
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Cryostat
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200530
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200531
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Parameter extraction
and
first results
Part III:
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200532
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
OFET
some differences to conventional OFETs– can potentially operate in electron and hole accumulation mode
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200533
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
OFET
basic OFET operation– related to a capacitor
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200534
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
OFET
output curve, logarithmic output curve, linear
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200535
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
green: Vd = 10V
cyan: Vd = 45V
Symobols:
different devices
300 K 150 K
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200536
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
Thank You for Your Attention!
University of Technology Graz - Institute of Solid State Physics
Professor Horst Cerjak, 19.12.200537
Andrej Golubkov Charge transport in organic semiconductors and [email protected]
transition between transport modes
Trap dominated Intrinsic