Carrier mobility of Si and Organic Materials

(1)

Organic Semiconductor EE 4541.617A 2009. 1^stSemester

2009 5 12

K. C. Kao and W. Hwang, Electrical Transport in Solids, (Pergamon, New York, 1981), p.159

Changhee Lee, SNU, Korea 1/41

Changhee Lee

School of Electrical Engineering and Computer Science Seoul National Univ.

[email protected] 2009. 5.12.

Electron mobility of Si

Carrier mobility of Si and Organic Materials

hole mobility of Perylene hole mobility of MPMP

Changhee Lee, SNU, Korea 2/41

370 nm thick perylene crystal 8.7 um thick unordered layer of

MPMP ( sublimed).

(2)

d

²

Mobility Measurement Techniques

10

⁻²

)

/ ( cm

²

Vs

μ 10

−4

10

⁻⁶

10

⁻⁸

10

⁰

10

²

TOF Mobility in the bulk

d = 0.5~5 mm

FET

Mobility in a thin layer d ~ 50 nm

μ τ V d

²

=

∴ V d τ = μ

²

d 0.5 5 mm

Other mobility measurement techniques

• Dark injection in the space-charge limited current regime

• I-V characteristics of space charge limited current

• Transient EL

• SHG measurement [T. Manaka, E. Lim, R. Tamura, M. Iwamoto, Nature Photon.1, 581–584 (2007).]

……

Mobility Measurement Techniques : Organic TFT

T. N. Jackson, Penn State U.

(3)

Light (hν)

μ τ V

d

²

= Mobility measurement techniques: TOF-PC

Time-of-flight photoconductivity t =0

hυ

-- - - - - ++ ++ ++

-- - - - -

++ ++ + +

0 < t

< τ

^-^-^-- - -

++ ++ + +

t

= τ

rrent

g p y

N₂laser

Vacuum Cryostat

B/S

Sample Si-PD

Trigger

t =0 t

= τ 0 < t

< τ Time

Photocu r

Oscilloscope Bias V

PC

gg

TOF Signal R_L

Transport of charge carriers in organic materials

60 40 20 0

Photocurrent (arb. units)

10 08 06 04 02 00

0.20 0.15 0.10 0.05 hotocurrent (arb. units) 0.00

a-NPD Alq3

Gaussian transport Dispersive transport Fast

Slow

P 1.00.80.60.40.20.0

Time (μs)

Ph 806040200

Time (μs)

Dispersive transport Gaussian transport

er Densit y

Trapping and release Band States

Distance

Carri e

Localized states

Hopping Deep trap

Ref.) Harvey Scher, Michael F. Shlesinger and John T. Bendler, Physics today, Jan. p.26 (1991)

(4)

Mobility Measurement Techniques: Transient EL

30

25

20

rb.unit)

57V

Al

PPP

15

10

5

0

Light (x10-3 ar

500 450 400 350 300 250 200 150 100 50 0

Time (x10^-9 s) 57V

19V 27V 39V 42V 46V 52V

240 220

Mobility from the delay time τ=d

²

/ μV

ITO glass

PMT

220 200 180 160 140 120 100

Time Delay (ns)

60 50 40 30 20 10

1/V (x10^-3 V^-1)

Hole mobility

in the vacuum-deposited PPP:

ITO/PPP/Al: μ=4.5x10

^-6

cm

²

/Vs

G. W. Kang, C. H. Lee, W. J. Song, and C. Seoul, SPIE 4105, 362 (2001).

Transient EL Mobility vs TOF-PC mobility in Alq3

S. C. Tse, H. H. Fong, and S. K. So, J. Appl. Phys. 94, 2033 (2003)

For a thin layer of Alq3 (d<180 nm), it is found that t_dis affected by both the charging effect and carrier transit time through the Alq3 layer. For a thicker layer of Alq3 (d>200 nm), t_d approaches the intrinsic electron transit time through Alq3 .

(5)

Space-charge-limited current

Hole only device

0.3 μm d=0.13 μm

0.7 μm

OC

₁

C

₁₀

-PPV

Electron only device

3 2

8 9

d J_SCLC= ε_oε_rμV

d=0 22 m

ITO + Au

OC

₁

C

₁₀

-PPV -

d=0.22 μm 0.37 μm

0.31 μm ² ¹

1 +

∝ ^m_m+

d J V

Ca (a) Ca

Poly(dialkoxy-p-phenylene vinylene) (OC₁C₁₀-PPV)

P. W. M. Blom M. J. M. de Jong, and J. J. M. Vleggaar, Appl. Phys. Lett. 68, 3308 (1996).

Organic Semiconductor EE 4541.617A 2009. 1^stSemester d

T it ti

V R

+ + + + + +

Dark injection SCL transient current

Transient SCLC

Transit time

Ohmic contact tp=

0 . 787 τ

PTPB

poly (tetraphenylbenzidine) PTPB 1.0

0.8

0.6

i(t) (arb. unit) 0.4

Dark injection SCL transient current τ

787 .

=0 tp

t

Changhee Lee, SNU, Korea 10/41

M. Abkowitz, J. S. Facci, and M. Stolka, Appl. Phys. Lett. 63, 1892 (1993).

0.2

0.00.0 0.2 0.4 0.6 0.8 1.0

Time (ms) 787 . 0

tp

τ= TOF-PC

S.C. Tse, S.W. Tsang, and S.K. So, J. Appl. Phys. 100, 063708 (2006).

(6)

Mobility Measurement Techniques: dark charge injection

ITO/300nm m-MTDATA/Ag with ITO biased positively.

E t

_tr

= 0 . 786 d

In a monopolar and single-layer configuration, the carrier transit time is shorter than in the absence of space-charge effects due to the enhancement of the electric field at the leading edge of the carrier packet.

tr

μ E

The transient current overshoots its steady-state value by a factor of 1.21 and starts at 0.44 times the

steady-state value.

Changhee Lee, SNU, Korea 11/41

M. Stossel et al, Phys. Chem. Chem. Phys.1, 1791 (1999) A. Many and G. Rakavy, Phys. Rev. 126, 1980 (1962)

nj.

Carrier injection efficiency

contact limiting - current for 1

contact ohmic for 1

current injected : efficiency Injection

<

=

= η

η

η SCLC 3

2

8 9

d J

_SCLC

= ε

^o

ε

^r

μ V

Injection Ef ficiency η

in

Hole

Hole Injection Barrier (eV)

M. Abkowitz, J. S. Facci, J. Rehm, J. Appl. Phys. 1998, 83, 2670.

(7)

Mobility Measurement Techniques: TRM-SHG

Vs cm

/ 25 .

0

²

=

μ

T. Manaka, E. Lim, R. Tamura, M. Iwamoto, Nature Photon.1, 581 (2007).

T. Manaka, M. Nakao, D. Yamada, E. Lim and M. Iwamoto, Optics Express 15, 15964 (2008).

(1) Poole-Frenkel Model

Conduction band x = x

^m

x

) (x V )

(x V

Charge Transport in Disordered Organic Solids

E e E

PF 2

/ 1

0 3

PF

β

φ πεε ⎟⎟ ⎠ =

⎜⎜ ⎞

⎝

= ⎛ Δ

Conductio n band edge at E Tunneling

φ

PF

edge at E=0 Δ

Zero field (E=0) E≠0

x

− eEx x

e

o

ε πε 4

−

2

Zero field (E 0) E≠0

⎟⎟ ⎠

⎞

⎜⎜ ⎝

⎟⎟ ⎛

⎠

⎜⎜ ⎞

⎝

⎛ − Δ

= k T

E T

k μ E

F,T

B PF B

PF

exp exp

)

( β

μ Δ E : Activation energy at

E=0

: PF Mobility : PF constant

μ

PF

β

PF 0

3

PF

πεε

β = e

(8)

0

1 1 1

T T

T

_eff

= − : Empirical parameter

T

0

(2) Gill’s modified Poole-Frenkel model

⎟ ⎟

⎠

⎞

⎜ ⎜

⎝

⎛

⎟ ⎟

⎠

⎞

⎜ ⎜

⎝

⎛ − Δ

=

eff

k T

E T

k μ E

F,T

B PF B

PF

exp exp

)

( β

μ

PVK

poly-n-vinylcarbazole (hole conductor)

N n

O2N C

O

NO2

TNF

2,4,6-trinitro-9-fluorenone (electron acceptor)

NO2

W. D. Gill, J. Appl. Phys. 43, 5033 (1972).

(3) Bassler’s Gaussian Disorder Model

• The energy of each site is distributed in accordance with the Gaussian distribution

• Energies of adjacent sites are uncorrelated and motion between sites is Markovian (no phase memory)

• The transition rates for phonon-assisted tunneling (Miller and Abrahams):

⎪⎬

⎪ ⎫

⎨

⎧ − >

− −

=v R ⁱkT ^j ⁱ ^j

W ε ε ε ε

α

) exp( ), 2

exp(

_ε^ε^j

Charge Transport in Disordered Organic Solids

α= inverse localization length, Rij = distance between the localized states, εi= energy at the state i.

• Since the hopping rates are strongly dependent on both the positions and the energies of the localized states,

hopping transport is extremely sensitive to structural as well as energetic disorder.

σ

LUMO

⎪⎭⎬

⎪⎩⎨

>

=

j i ij j

ph

ij v R kT

W α ε ε

, 1 ) 2

exp(

_ε_i

A. Miller, E. Abrahams, Phys. Rev.120(1960) 745. Hopping

0 5

ε

Changhee Lee, SNU, Korea 16/41

H. Bässler, Phys. Status Solidi B 175, 15 (1993).

HOMO

σ

-1 0 1 2 3 4 5

-10

-5 ^kB^T ^kB^T

σ2

ε^∞ =−

log (t/t

_o

)

T k_B

ε

(9)

T k_B σ =^∧ σ

Hole mobility of TAPC embedded in BPPC matrix

: Energetic disorder : Positional disorder : Constant 2 9x10^-4(cm/V)^1/2 σ

CΣ

radius on localizati carrier and

distance site - inter average where

), / 2 exp(

)

( ²

=

−

=

o

o o

o a

μ ρ

ρ

ρ ρ ρ ρ

H. Bässler, Phys. Status Solidi B 175, 15 (1993). M. Stolka, J. F. Janus and D. M. Pai, J. Phys. Chem. 88, 4707 (1984).

1.5) ( 3 ,

exp 2 3 exp 2 ) (

1.5) ( 3 ,

exp 2 3 exp 2 ) (

2 2

B 2

B

2 2

B 2

B

≥

⎪⎭ Σ

⎪⎬

⎫

⎪⎩

⎪⎨

⎧

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡ ⎟⎟⎠ −Σ

⎜⎜ ⎞

⎝

⎛

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡

⎟⎟⎠

⎜⎜ ⎞

⎝

−⎛

=

<

⎪⎭ Σ

⎪⎬

⎫

⎪⎩

⎪⎨

⎧

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡ ⎟⎟⎠ −Σ

⎜⎜ ⎞

⎝

⎛

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡

⎟⎟⎠

⎜⎜ ⎞

⎝

−⎛

=

T E C k T μ k E,T

o o

σ μ σ

: Constant ~2.9x10^-4(cm/V)^1/2 : High temperature limit of the mobility C

μo

P. M. Borsenberger, L. Pautmeier and H. Bassler, J. Chem. Phys. 94, 5447 (1991).

MPMP

bis(4-N,N-diethylamino-2-methylphenyl)-4- methylphenylmethane

(thickness~8.7 μm) Hole mobility of MPMP

Charge Transport in Disordered Organic Solids

P. M. Borsenberger, L. Pautmeier and H. Bässler, J. Chem. Phys. 95, 1258 (1991)

(10)

Organic Semiconductor EE 4541.617A 2009. 1^stSemester Disorder parameters

•σ: The width of the DOS. Random distribution of both permanent and van der Waals dipoles lead to local fluctuations in electric potential Æincrease σby an amount proportional to the square root of the dipole concentration and to the strength of the dipole moment. Æreduce the carrier mobility. The smaller dipolar interaction is better for the carrier transport.

•Σ: The degree of positional disorder. Amorphous morphology of molecular solids or doped polymers lead to the variation in the intermolecular distances.

Disorder parameters

μ TAPC doped polystyrene>> μ TAPC doped polycarbonate

Dipole moment:

• TAPC [1,1-bis(di-4-tolylaminophenyl)cyclohexane] = 1.0 D

• PC (bisphenol-A-polycarbonate) = 1.0 D

• PS (polystyrene) = 0.1 D

• Larger dipolar interaction increases both σand Σ.

• The elimination of random dipolar fields due to

P. M. Borsenberger and H. Bässler, J. Chem. Phys. 95, 5327 (1991).

• The elimination of random dipolar fields due to static dipole moments of PC reduces both σand Σ and thereby increases the mobility.

Disorder parameters

A. Dieckmann, H. Bässler and P. M. Borsenberger, J. Chem. Phys. 99, 8136 (1993).

(11)

Effect of dipolar molecules on carrier mobilities

• Conduction through the dopant.

• Mobility is strongly affected by the dipole moment of the dopant for holes and electrons

Changhee Lee, SNU, Korea 21/41

A. Goonesekera and S. Ducharme, J. Appl. Phys. 85, 6506 (1999)

Temperature dependence of the hole mobility of PPVs

P.W.M. Blom, M.C.J.M. Vissenberg, Materials Science and Engineering 27, 53-94 (2000)

(12)

⎩ ⎨

⎧ <

=

₋⁻ ₊⁻

τ

α α

t t

t

t ,

(t)

J

₍₁ ₎

) 1 ( ph

(4) Scher-Montroll dispersive transport model

Trapping Band States

−

α

≈ Ψ ( t ) t

Continuous time random walk (CTRW)

⎩ t

⁽¹⁺^α⁾

, t > τ

pp g

p

and release Localized states

Deep trap

T

o

= T α Disappearance of plateau

h otocurrent

Slope = -(1- α)

log i

ph

τ ( )

α¹

E

∝ L

Time

t =0 t =τ Time

P h

Slope = - (1+α)

log t

t =0 t =τ

Scher and Montroll, Phys. Rev. B 12, 2455 (1975)

τ ( )

α¹

E

∝ L

Scher-Montroll model of dispersive transport

) 45 . 0 1 (−

t

−

) 45 . 0 1 (+

t

−

2 . 2

45 . 0 1 1

= α=

H. Scher and E. W. Montroll, Phys. Rev. B 12, 2455 (1975)

(13)

Dispersive Transport in a-Selenium

G. Pfister, Phys. Rev. Lett. 36, 271 (1976)

Changhee Lee, SNU, Korea

26/41

(14)

Charge –voltage characteristics of organic semiconductors

Injection limited

Thermionic emission

] 1 )

[exp( −

= k T

J eV J

B

s ^* ²

exp( )

T k T e

A J

B bn s

φ

= −

Current

Bulk Limited

Ohmic (Doped semiconductor) E

ep J = μ Tunneling

)

2

exp(

E E b

J ≈ −

qh q b m

3 ) ( 2

8 π

^*

φ

³^/²

=

Bulk Limited

SCLC (undoped semicond. or Insulator)

3 2

8 9

d J

_SCLC

= ε

_o

ε

_r

μ V

PPV

Au ITO

V=0

V>0

Space-charge-limited current (SCLC)

velocity density)

charge (

J

_SCLC

≈ ×

Space-charge-limited current (SCLC) OLED acts as a capacitor

V>0

V>>0 +

PPV

Au ITO +

+ + +

+ + + + +

2

) ( area ) (

velocity density)

charge (

V d V V d d E

CV J

r o

r o SCLC

μ ε ε

ε μ ε

μ

⋅

=

⋅ ×

=

ε

− ρ

2

=

2

dx V d

potential

Field ~ 0 at contact

+

PPV Au

ITO + + +

+ +

+ + + +

+ + +

+ + + +

+

3

d

r

=

o

3 2

8 9

d J

_SCLC

= ε

_o

ε

_r

μ V

x d ohmic

SCLC

(15)

Ohmic Contact (1)

field.

applied external no is there since

, 0 :

equation flow Current

.

: equation Poisson

dx F - qD dn qn J

qn dx dF

=

= μ ε

figure right in the condition boundary

the From

log

used.

is relation

Einstein the where

, pp

0

Fdx . T k

q n

n

q T k μ D T Fdx k Fdx q D

μ n dn

x

B s

B B

=

∴

=

∴

∫

: cathode virtual

law.

Boltzmann i.e.,

], exp[

figure, right in the condition boundary

the From

0

T k

χ) ψ(x)-(φ n

n

. Fdx q χ) ψ(x)-(φ

B s m

x m

− −

=

∴

−

=

− ∫ .

dx dV 0

: cathode virtual

=

when 0 condition boundary

the using and

) 2(

g multiplyin after

sides both g Integratin

].

exp[

2 2 2

2

χ φ dψ ψ

dx dψ T k

χ) ψ(x)-(φ n

q n q dx qdF dx

ψ d

B m s

−

=

− −

−

=

−

=

−

=

ε ε

Ohmic Contact (2)

2 )}].

{exp(

2 sin 2 )[

exp(

2 ) ( W

region on accumulati the

of width the

gives equation this

g Integratin

]}.

exp[

] {exp[

) 2 (

, when

0 condition boundary

the using and

1 2

/ 1 2

2 2

T k

φ T

k χ φ N

q T k

T k

) φ ( T

k χ) ψ(x)-(φ T

k n q dx dψ

χ φ dx ψ

B m B

c B

B m B

m B

s

− −

=

− −

−

=

−

ϕ

π ε

ϕ ε

Changhee Lee, SNU, Korea 30/41

2 ).

exp(

2 ) 2 ( W

, level energy discrete a in confined traps shallow containing tors

semiconduc For

2 ).

exp(

2 ) 2 ( W

, 4 If

2 / 1 2

T k

E χ φ N

q T k

E T

k χ φ N

q T k

T k φ

B t t

B

t B

c B

B m

−

≈ −

>

−

ε π

ε

π

ϕ

(16)

Space-charge-limited current

.) ( ) ( :

equation flow Current

)] . ( ) ( [ )

( : equation Poisson

density trap of function on Distributi

x F x p q J

x p x p q dx

x dF (E)S(x).

N h(E,x)

p

t t

μ ε ε

ρ

=

= +

=

φ

oⁱ

'

eV

'

x eVa

0 : electrode Virtual

'

=

=x

dxx

dφ

) 2 (

2 . )]

( [ )]

0 ( [ )]

( [ 2 . )]

( [ ) ) ( ( 2

, 0 ) ( For

. exp

, ) ( )

(

) ( ) ( q

2 2

J x x F

J x x F x

F x J F

dx x F d dx

x x dF F

x p

T ] k [ E N p(x) dE E h(E,x)f x

p

p q

p p

t

B F v

E

E p

t

p

u p l

εμ εμ

μ

=

∴

=

−

∴

=

−

=

= ∫

Electrode

Organic semiconductor Electrode

Changhee Lee, SNU, Korea 31/41

law.

Gurney - Mott 8 .

9

) ( condition,

Boundary . )

(

3 2

0

d J V

. dx x F V x x

F

p

d p

εμ εμ

=

∴

∫

The distance Wabetween the actual electrode surface and the virtual anode (-dV/dx=F=0) is so small that we can assume F(x=WaÆ0)=0for simplicity.

(no trap)

ITO/PPV/Au hole-only devices

3 2

8 9

d J

_SCLC

= ε

_o

ε

_r

μ V

3

&

/ 10 5 0 i

Fit

⁻⁶ ²

V

3

&

/ 10 5 . 0 using

Fit μ = ×

⁶

cm

²

Vs ε

_r

=

⎟⎟⎠

⎞

⎜⎜⎝

⎛ Δ −

−

=

eff B oexp PF

)

( k T

F μ E

F,T β

μ

(17)

of onset or the law s Ohm' from departure the of onset The

8 . 9

such that t predominan is

specimen the

inside carriers free

generated thermally of

density the if holds law s ohm' field, low At

3 2 p p

o

d V d

qp V

p

εμ μ

>>

J log

V V at ansit time

carrier tr when the place takes

regime SCL the to ohmic the from n transitio the Therefore,

. or 8 9 8

9 V

have e equation w this

g rearrangin By

9 . V 8 when place takes conduction SCL

the

2 t d t 2

2

o p o p

o

d qp

d

d qp

τ τ σ τ

ε μ ε μ

ε

=

≈

=

Ω Ω

Ω

V J ∝

V

2

J ∝

. time relaxation dielectric

the to equal ely approximat is

V

d o p

σ τ ε μ

=

Ω

K. C. Kao and W. Hwang, Electrical Transport in Solids, (Pergamon, New York, 1981), p.159

t.

predominan is

conduction SCLC

, At

t.

predominan is

conduction ohmic

, At

d t

τ τ

<

> ε

2

9 V 8 qp

_o

d

Ω

= log V

0

, equation

Continuity

. time relaxation

dielectric

_d

σ τ ε

t J ) p q (p

^o

o

⋅

−∇

∂ = +

∂

=

ignored.

be can term 2nd the , time relaxation dielectric

the to comparable

time a in specimen over the

uniformly spreads

p and If

. )

(

).

( )

( J by given is current where

d 2

μ

σ τ ε ε

μ

qp p p

p D qp p

t p

p p qD F p p q t

o o

p p

o p p o

∂

=

<

∇ +

−

∂ =

∴ ∂

+

∇

− +

=

∂

m.

equilibriu establish

- re carrier to for the

required time the of measure a is

. exp 0

. ) ( τ

d

ε τ

μ p p(t) p(t ) (-t/ ) qp

t p

d p

o

∴ = =

−

∂ ≈

∴ ∂

(18)

) , ( / 1

) ) (

( density charge

Trapped

) ( ) ( ) , (

levels energy discrete

multiple or

single in confined Traps

x p N

x S x N

p x S E E N x E h

t t t t

t t

θ δ

≈ +

−

=

traps of on distributi spatial

uniform -

non Ignoring

8 . 9

. where

) ( / 1

3 2

d θ V J

N e N θ g

x p N

eff t r o SCLC

kT E

t v p t

t t

t

μ ε ε

θ

=

+

−

E

_CB

8 . 9

,

3 2

d θ V J

d p d

p θ p

t r o SCLC

eff t t

μ ε ε

= + =

=

E

_VB

Discrete trap levels

Changhee Lee, SNU, Korea

36/41

(19)

DOS Energy

Space-charge-limited current: analytic solution

kT E E c f

F c

e N n

− −

=

c c

E

kT FD E E t

t

e f E dE

T k n N

∞

−

− −

= ∫ ( )

E

_C

(E

_LUMO

) E

_F

t c

kT E E

t t

e

kT E N G

− −

= ) ( E

t F c

F c

kT E E t

E kT

E E

t B

t t B

e N

dE T e

k N

T k

− −

∞

−

− −

∞

=

≈ ∫

∫

T 1

kT

t

Exponential trap distribution

T m T

N N n N

N n n

t

m c f t T T

c f t

t ^t

=

≈

∴ ( ) ( )

¹

N J N d

x F dF

x F x n q J

N qN n x x qn n x n q dx

x dF

t m m

f

m c f o

t o t o

t f

=

≈ + ≈

=

/ 1 /

1

/ 1

. ) ) (

(

.) ( ) ( : equation flow Current

. ) ) (

)] ( ( ) ( ) [ ( : equation Poisson

μ

ε ε ε ε ε

ε log J

Law Gurney Mott

Space-charge-limited current

. dx x F V

N q

J N m x m F

N x q

J F N

m m

N q dx

d m c m

m

o t

m c o m t m

c o

∫

=

= +

∴ + =

∴

+ +

+

0 1 1 1

/ 1 1

) ( condition, Boundary

. ) ( 1 ) ( ) (

. ) 1 (

) (

μ ε ε

3 2

d V 8 J 9

Law Gurney - Mott

εμ

=

. , 1 )

( 1 )

1

( 2

₂ ₁

1 1

1

T m T d

V N m

m m

N m q

J

_m ^t

m m t m o

c

m

=

+ +

=

⁻

μ +

⁺

ε ε

⁺₊

V

Ω

log V

0

V

TFL

. 1 ) 2 )( 1 ( 1 ) (

SCLC Trapped

Ohmic

1 2 1

m m m

v o r o

t

m m m m N

p N V qd

+

Ω +

+

= +

⇒ ε

ε ^[₈⁹ ⁽ ¹⁾ ⁽₂ ¹₁⁾ ^] ^.

SCLC free - Trap SCLC Trapped

1 1 1 2

+ −

+ +

= +

⇒

m m m v m t r o

TFL m

m m m N N V qd

ε ε

(20)

Ca/PPV/Ca electron-only devices

Trap-limited SCLC Trap-free SCLC

Changhee Lee, SNU, Korea 39/41

. , SCLC limited - Trap

1 2

1

T m T d N V N

J

_m ^t

m m t

v

=

∝ μ

⁻ ⁺₊

3 18

eV 15 .

≈ 0 E

t

SCL current with an exponential trap distribution

3 -

18

cm

≈ 10 N

t

P. E. Burrows, Z. Shen, V. Bulovic, D. M. McCarty, S. R. Forrest, J. A. Cronin and M. E. Thompson, J. Appl. Phys. 79, 7991 (1996).

(21)

Trap-limited SCL current with field-dependent μ

W. Brütting, S. Berleb and A. G. Mückl, Org. Electronics 2, 1 (2001)