°
ǽ Ê m Ö «Y c lM ø n Ú; c 8 ý X ¢ ¥M ® o° Ë Ñ T ~ ¾© < gX c lÊ ÝX N Ë8 ý Copper(II)-Phthalocyanine ¤V R Ë ì Å
»Q + ä · ~ ç ¡ ç ¡Ù v · »g ` @\ 8 ; · = * å ¼ ÿ · % + Ö <
ç
H í ß @ / < Æ § Ó ü t o < Æõ , ç H í ß 573-701
(2011¸ 10 Z 4 17{ 9 ~ Ã Î6 £ §, 2011¸ 11 Z 4 7{ 9 Ã º& ñ : r ~ Ã Î6 £ §, 2011¸ 12 Z 4 1{ 9 > F S X & ñ )
\ P
S X í ß 7 £ x à Ìl Õ ü t` ¦ s 6 x # ITO/glass l ó ø Í 0 A\ Ä »l ì ø Í ¸^ copper(II)-phthalocyanine (Cu- Pc) õ Alq3\ ¦ ] X ½ + Ëô Ç 10 × 12 mm
2ß ¼l _ ~ à Ì} + þ A ITO/Cu-Pc/Alq3/Al Ä »l µ 1 Ï F g s ¸× ¼ (organic light emitting diodes : OLED)\ ¦ ] j % i . ITO F G 0 A\ & h 8 £ x ) a Cu-Pc ü < Alq3_ ¿ ºa H y y
5 nm, 50 nm s ? / Ð 10
−6Torr s _ / B N ì r 0 Al \ " f 7 £ x Ã Ì % i . s M : Cu-Pc H l ó ø Í _
: r ¸\ ¦ © : r õ 100
◦C _ ¿ º 7 á x À Ó_ : r ¸ Ð ½ ¨ì r # y y & h 8 £ x % i . & h 8 £ x ô Ç ~ à Ì} _ þ j& h ¸
|
` ¦ ¹ 1 Ôl 0 AK : £ ¤$ í _ 8 £ ¤& ñ É r X- r] X ì r$ 3 © u (X-ray diffraction ; XRD), > ~ ½ Ó Å Ò d
&
³p â (field emission scanning electon microscopy ; FE-SEM), F gf ¨ Ã º ¸ 8 £ ¤& ñ © u (UV-VIS-NIR spectrometer)\ ¦ s 6 x % i . Cu-Pc_ ¿ ºa \ É r ITO/Cu-Pc/Al _ À Ó- · ú : £ ¤$ í ¸ ¸ % i .
Ù þ
d # Q: Copper(II)-phthalocyanine (Cu-Pc), \ P S X í ß 7 £ x à Ìl Õ ü t, Ä »l µ 1 Ï F g s ¸× ¼, organic light emitting diode (OLED)
Study on the Copper(II)-phthalocyanine Characteristics for an OLED Fabrication Process
by Using Thermal Evaporation Deposition Techniques
Mijoung Kim · Sangbaek Kang · Hyonsook Kim · Youngan Chae · Deokjoon Cha ∗
Department of Physics, Kunsan National University, Gunsan 573-701 (Received 17 October 2011 : revised 7 November 2011 : accepted 1 December 2011)
By using thermal evaporation deposition techniques, we fabricated organic light emitting diodes (OLED) of (+)ITO/Cu-Pc/Alq3/Al(-) with sizes of 10 × 12 mm
2. The thickness of Cu-Pc and Alq3, respectively, were about 5 nm and 50 nm. For high-quality OLEDs fabricated under optimum conditions, the characteristics of copper(II)-phthalocyanine (Cu-Pc) thin films were measured by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-VIS- NIR spectrometry. The Cu-Pc thin films were prepared with two kinds of samples, samples prepared at room temperature and these prepared using a pre-heating temperature of 100
◦C. The current- voltage (I-V) curves of the (+)ITO/Cu-Pc/Al(-) layers were measured for different thicknesses of the Cu-Pc films.
PACS numbers: 72.80.Le
Keywords: Cu(II)-phthalocyanine, Organic light emitting diode (OLED), Thermal evaporation deposition techniques
∗
E-mail: [email protected] -1150-
Eastman Kodak _ W. Tangõ S. A.
VanSlyke s tris-(8-hydroxyquinoline) aluminum (Alq3) ü
< TPD H Ä »l Ó ü t é ß ì r \ ¦ 6 x # µ 1 Ï F g8 £ x õ Ã
º5 Å x8 £ x ~ Ã Ì} ] X ½ + Ë` ¦ + þ A$ í # 0 l qÒ o_ µ 1 Ï F g è \ ¦ ] j ô
Ç s Ê ê s \ ¦ © 6 x o H ¸§ 4 s r ÷ &% 3 [5].
Ä
»l Ó ü t × æ Copper(II) Phthalocyanine (CuPc) [6] H Z
} É r hole s 1 l x ¸\ ¦ & ñ / B N Å Ò{ 9 8 £ x(hole injection layer) Ó ü t| 9 Ð \ P & h Ü ¼ Ð ¸ î ß & ñ $ í s e # Q ´ ú § É r ½ ¨
' ÷ &# Q M ® o [7,8]. 7 £ ¤, CuPc Ä »l o½ + ËÓ ü t É r p-+ þ A ì ø Í
¸^ : £ ¤$ í ` ¦ t ¦ e Ü ¼ 9 ] X ½ + Ë r è _ µ 1 Ï F g · ú
`
¦ ± ú 2 X Ä »l µ 1 Ï F g è _ $ í 0 p x` ¦ Z } # Ä »l µ 1 Ï F g è _ Ã
º" î õ î ß & ñ $ í ` ¦ ¾ Ó © r v H X < l # ô Ç . s Qô Ç : £ ¤$ í
É r CuPc Ä »l µ 1 Ï F g è (OLED), Ä »l ~ Ã Ì} à Ô ½ t Û ¼ '
(organic thin Film transistor (OTFT), Ä »l I ª t (organic solar cell) ü < Û ¼G ' p" f(gas sensor) 1 p x _ ª ô Ç
è \ 6 £ x6 x 0 p x$ í s H Ó ü t| 9 s . ¢ ¸ô Ç Cu-Pc H Ä »l Ó
ü
t ç ß _ ] X ½ + Ë ÷ r ë ß m Á ºl Ó ü t ì ø Í ¸^ , F K5 Å q, ] X ^ 1
p
x õ _ ] X ½ + Ë è \ @ /ô Ç > hµ 1 Ï\ ¸ Ö ¸6 x ½ + É Ã º e # Q \ V\ ¦ [
þ
t # Q MISFET(metal insulator semiconductor field effect transistor) è ü < ° ú s : £ ¤ s ô Ç À Ó · ú : £ ¤$ í ` ¦ ° ú H 6
£
x6 x ½ ¨ ¸ Ö ¸ µ 1 Ïy ' ÷ &# Qt ¦ e [9].
: r 7 Hë H \ " f H p-type Ä »l ì ø Í ¸$ í Ó ü t| 9 Cu(II)
Phthalocyanine (Cu-Pc)õ n-type Ä »l ì ø Í ¸$ í Ó ü t| 9
Alq3` ¦ ITO/glass l ó ø Í 0 A\ \ P 7 £ x Ã Ì ~ ½ ÓZ O (Thermal evaporation deposition) Ü ¼ Ð $ í © # (+)ITO/Cu- Pc/Alq3/Al(-) ~ à Ì} + þ A p/n ] X ½ + Ë Ä »l µ 1 Ï F g s ¸
×
¼(Organic light emitting diodes; OLED)\ ¦ 10
−6Torr s _ / B N ì r 0 Al \ " f 7 £ x Ã Ì # ] j % i Ü ¼ 9 s
M : Cu-Pc H l ó ø Í_ : r ¸\ ¦ © : r õ 100
◦C _ ¿ º 7 á x À
Ó_ : r ¸ Ð ½ ¨ì r # y y & h 8 £ x % i . ¿ ºa 8 £ ¤& ñ l
Ð Cu-Pc H 5 nm, Alq3 H 50 nm ? /ü @_ ¿ ºa Ð & h 8 £ x
% i Ü ¼ 9 ¿ ºa \ É r ~ Ã Ì} _ & ñ $ í © : £ ¤$ í ` ¦ 0 AK FE-SEM, XRD, UV-VIS F g: £ ¤$ í 1 p x` ¦ ¸ % i Ü ¼ 9 s
\ É r I-V : £ ¤$ í , F g À Ó : £ ¤$ í ` ¦ ¸ % i . hole injection 8 £ x Ü ¼ Ð" f_ Cu-Pc_ : £ ¤$ í ` ¦ 5 nm \ " f 30 nm _ É r 7 á x À Ó_ ¿ ºa \ ITO/CuPc/Al ] X ½ + Ë` ¦ + þ
A$ í # À Ó- · ú : £ ¤$ í ¸ ¸ % i .
Fig. 1. Molecular structure of (a) Cu-Pc and (b) Alq3.
II. ÷ m Ç ] M ö
Cu-Pc H C
32H
16CuN
8_ ì r ½ ¨ ¸\ ¦ t ¦ e .
Fig. 1(a) % ! 3 Cu-Pc H × æd \ F K5 Å q Cu s : r s 4> h_ | 9
èü < ½ + Ë ) a ¨ î ½ ¨ ¸\ ¦ s À Ò 9 D4th @ /g A$ í ` ¦ ° ú H
&
ñ ì r [ þ t s [10]. Cu-Pc ~ Ã Ì} É r α, β, γ, X - type 1 p x _
#
Q t & ñ _ ½ + Ë ½ ¨ ¸ Ð · ú 94 R e . © ¸ ú
· ú
9 ½ + ˽ ¨ ¸ Ð H \ P & h Ü ¼ Ð ï r î ß & ñ & h α-phaseü <
\ P
& h Ü ¼ Ð î ß & ñ & h β-phase e [11–14]. 0 l q H : r ¸
H 600
◦C s .
Alq3 H Fig. 1(b) ü < ° ú s C
27H
18N
3O
3Al _ ì r ½ ¨ ¸
\
¦ ° ú H . Cu-Pcü < q 5 p w > × æ © \ · ú À Òp ³ o u (Alu- minum) Al s 0 Au " f 3> h_ | 9 èü < 3> h_ í ß è
½
+ Ë÷ &# Q e . @ / Òì r OLED _ µ 1 Ï F g É r Alq38 £ x \ " f { 9 # Q
9 Alq3_ 0 l q H : r ¸ H 415
◦C s [15].
Ä
»l Ó ü t ì ø Í ¸^ H { 9 ì ø Í& h Ü ¼ Ð Á ºl ì ø Í ¸^ _ \
-t @ /% i ¸@ /(conduction band)\ K { © H LUMO(Lowest Unoccupied Molecular Orbital) ü <
@ /(valance band) \ K { © H HOMO(Highest Occupied Molecular Orbital) y y 0 Au # Cu-Pcü <
Alq3 ü < ° ú É r © s ô Ç ì ø Í ¸^ Ó ü t$ í _ ] X ½ + Ë \ " f_ band gap _ Ð ) a · ú \ _ K µ 1 Ï F g s { 9 # Qè ß .
Cu-Pc ü < Alq3_ y y \ @ /ô Ç HOMO H 4.95 eV, 5.8 eV s ¦ LUMO 1.7 eV, 3.1 eVs . { 9 & ñ s © _ · ú
\
" f holeõ _ recombinations Ò q tl ¦ LUMOü <
HOMO gap s _ \ -t s \ K { © H exciton \ - t
Ð µ 1 Ï F g > ) a . Fig. 2(a) H $ ½ Ós 20 Ω/cm
2s
¦ ¿ ºa 150 nm ITO H ª F G(anode), Cu-Pc H ¢ - a Ø
æ8 £ x Ü ¼ Ð & ñ / B N` ¦ Å Ò{ 9 H 8 £ x s 9 Alq3 µ 1 Ï F g8 £ x s .
Al s 6 £ §F G(cathode) Ü ¼ Ð ITO/CuPc/Alq3/Al è _ ] X
½
+ Ë \ " f_ 1 l x " é ¶ o \ ¦ Ð# ï r . ITO H y n Cs ü @Â Ò Ð µ
1 Ïí ß H / B M Ü ¼ Ð 4.3 eV_ { 9 < ÊÃ º (work function)\ ¦ t
9 Al É r 4.2 eV _ q §& h ± ú É r { 9 < ÊÃ º\ ¦ ° ú ¦ e .
Figure 2(b) H Ä »l µ 1 Ï F g è _ \ -t ï r 0 A\ ¦ Ð# ï r
.
Fig. 2. (a) Exciton formation mechanism of ITO/
CuPc/Alq3/Al. (b) Energy-level diagram of OLED.
Fig. 3. (Color online) Schematic structures of OLED.
: r z ´+ « >\ " f H ) í Û ¼J $ \ P s y | ¿ º> h_ É r ¸
m
\ Cu-Pcü < Alq3 20 mg s ? / Ð è| ¾ Ó_ r « Ñ\ ¦ y y {
¦ ∼10
−6Torr _ / B N ¸\ ¦ Ä »t " f [ j' ) a 15 × 15 mm
2ß ¼l _ © 6 x ITO/glass l ó ø Í\ \ P 7 £ x à Ìr & ~ Ã Ì }
` ¦ ë ß H . ¸m ü < l ó ø Í t _ o H 35 cms 9, ¿ ºa 8 £ ¤& ñ G ' p" f t _ o ¢ ¸ô Ç 35 cm Ð [ O u
%
i . ~ à Ì} _ ¿ ºa 8 £ ¤& ñ É r thickness monitor (TM 400- Maxtek)\ ¦ s 6 x % i Ü ¼ 9 7 £ x Ã Ì ¿ ºa x 9 7 £ x Ã Ì 5 Å q ¸\ ¦ ¸ ] X
% i . ~ Ã Ì} _ & h 8 £ x 5 Å q ¸ H 0.3 - 0.6 ˚ A/sec ÷ & ¸2 ¤
#
Ä »l ì ø Í ¸^ ~ Ã Ì} ` ¦ í H & h Ü ¼ Ð ë ß [ þ t% 3 . 9 כ ¹\
& h ` ¦ ß ¼> ½ + É â Ä º H ITO & h 8 £ x ) a ó ø ÍÄ »o \ ¦ 6 x
# J õ \ g A` ¦ f ] X ô Ç Û ¼ß ¼\ ¦ s 6 x # & h 8
£ x % i .
: r z ´+ « >\ " f OLED ] j r Cu-Pc H 5 nm, Alq3 H 50 nm, Al É r 120 nm _ ¿ ºa Ð © : r õ 100
◦C Ð heating ô Ç
¿
º 7 á x À Ó_ r « Ñ\ ¦ ] j % i . ¢ ¸ô Ç Z > ¸ Ð F g f ¨ Ã º 8 £ ¤& ñ 6
x r « Ñ_ l ó ø Í É r slide glass Ð % i ¦, l & h : £ ¤$ í 8 £ ¤
&
ñ 6 x r « Ñ_ l ó ø Í É r ITO ~ Ã Ì} s ïh A ) a glass\ ¦ 6 x
%
i . ] j ) a OLED è _ ½ ¨ ¸ H Fig. 3 õ ° ú Ü ¼ 9
)
a · ú \ _ K y n C É r ITO/glass Ü ¼ Ð µ 1 Ï F g ô Ç .
s
X O > ] j ) a OLED \ @ / # & h 8 £ x ô Ç ~ Ã Ì} _ : £ ¤$ í
`
¦ X- r] X ì r$ 3 © u (X-ray diffraction ; XRD, Model : X’pert-pro MPD, PANalytical, Netherlands), >
~
½ Ó Å Ò d & ³p â (field emission scanning electon microscopy ; FE-SEM), F gf ¨ Ã º ¸ 8 £ ¤& ñ © u (UV-VIS- NIR spectrometer)\ ¦ s 6 x # ¸ % i Ü ¼ 9 OLED_
Fig. 4. X-ray diffraction patterns of Cu-Pc thin films deposited at room temperature and substrate heating temperature 100
◦C.
À Ó · ú : £ ¤$ í _ 8 £ ¤& ñ É r Keithley 487 Voltage Source ü <
196 System DMM` ¦ Ö ¸6 x % i . Cu-Pc_ ¿ ºa \ É r ITO/CuPc/Al _ À Ó- · ú : £ ¤$ í ¸ ¸ % i .
III. ÷ m Ç] M ö+ s ÇÊ Ý õ m Í w ² o
Figure 4 H l ó ø Í_ : r ¸\ ¦ © : r \ " f 7 £ x à Ìô Ç ~ à Ì} õ 100
◦
C Ð ¦& ñ # $ í © ô Ç Cu-Pc ~ Ã Ì} _ X- r] X J s
. s M : 6 x ô Ç X- É r Cu _ α (λ = 1.5405 ˚ A) s % i ¦,
r] X y É r 5
◦≤ 2θ ≤ 55
◦_ 8 £ ¤& ñ % ò % i \ " f ¸ % i .
© : r \ " f 7 £ x à Ìô Ç ~ à Ì} _ â Ä º r] X y 23
◦≤ 2θ ≤ 28
◦#
3 0 A_ % ò % i ` ¦ Ð 4> h_ r] X x ß ¼(diffraction peak)[ þ t s
& ñ S X y H X < s כ É r Berger1 p x [16,17] s Ð ¦ô Ç
?
/6 x _ α-phase monoclinic ½ ¨ ¸_ (200), (111), (112), (312) ü < (313) õ { 9 u H כ ` ¦ · ú Ã º e % 3 .
l
ó ø Í` ¦ 100
◦C \ P " f 7 £ x à Ìô Ç â Ä º_ X- r] X
É r β-phase _ ~ Ã Ì} s + þ A$ í ÷ &# Q α-phaseü < β-phase mon- oclinic ½ ¨ ¸ D ¥ F ¦ e H כ ` ¦ ^ ¦ Ã º e . α-phase (200) É r # y y © ô Ç peak\ ¦ t 9 (113), (114) 1 p x _
β-phase peak[ þ t s D h Ðî r ³ ð & ñ ½ ¨ ¸\ ¦ + þ A
$ í
< Ê` ¦ S X % i .
{ 9
ì ø Í& h Ü ¼ Ð β-CuPc H P21/c < Ê É r P21/a monoclinic
½
¨ ¸\ ¦ ° ú Ü ¼ 9 unit cell ½ ¨ ¸ H a = 13.088 ˚ A, b = 4.777
Fig. 5. FE-SEM morphology of Cu-Pc thin films de- posited at (a) room temperature and (b) substrate heat- ing temperature 100
◦C.
˚ A, c = 11.021 ˚ A, β = 107.73
◦s ¦ α-Cu-Pc_ & ñ ½ ¨ ¸
H tetragonal ½ ¨ ¸ x 9 orthorhombic ½ ¨ ¸ü < monoclinic
½
¨ ¸ כ Ü ¼ Ð ¸ ÷ &# Q e Ü ¼ f S X z ´ô Ç ½ ¨ ¸& h : £ ¤
$ í
s µ 1 ß) 4 R e t H · ú §Ü ¼ 9 [10,18] unit cell ½ ¨ ¸ H a = 10.972 ˚ A, b = 12.148 ˚ A, c = 8.754 ˚ A, β = 90
◦ Ð · ú 94 R e
[19].
XRD z ´+ « > õ ÐÂ Ò' l ó ø Í : r ¸\ \ P & h Ü ¼ Ð Ô ¦ î ß
& ñ ô Ç α-phase\ " f î ß & ñ ) a β-phase Ü ¼ Ð © s { 9 # Q
H כ ` ¦ · ú Ã º e .
Figure 5 H l ó ø Í_ : r ¸\ ¦ © : r \ " f 7 £ x à Ìô Ç ~ à Ì} õ 100
◦
C Ð ¦& ñ # $ í © ô Ç Cu-Pc ~ Ã Ì} _ FE-SEM_ ³ ð s
. © : r _ ³ ð É r = å Q s [ tØ ¦ ) a x p × ¼ ¢ ¸ H ª ô Ç l Ñ
ü
æ + þ AI Ð $ í © ÷ &# Q e 6 £ §` ¦ ^ ¦ Ã º e Ü ¼ 9 ì ø Í 100
◦C Ð
\ P ô Ç Cu-Pc_ ³ ð É r { 9 & ñ ô Ç grain[ þ t s ¾ º0 > e H
&
ñ + þ AI \ ¦ & 6 £ §` ¦ · ú Ã º e % 3 .
OLED _ ] j \ e # Q" f ¢ - aØ æ8 £ x % i ½ + É` ¦ H Cu-Pc _
¿
ºa H Alq3 ü <_ ] X ½ + Ë \ " f_ µ 1 Ï F g _ [ jl \ ¦ & ñ H
×
æ כ ¹ô Ç כ ¹ s ) a . OLED\ ¦ ë ß [ þ t l 0 AK Alq3ü < ] X
½
+ ˽ + É Cu-Pc_ ¿ ºa -Á º ¿ º 0 >t ITO/glass A á ¤ Ü ¼
Ð È Òõ K ½ + É Alq3\ " f µ 1 Ï F g H y n Cs é ß ÷ &# Q µ 1 Ï F g
Fig. 6. (Color online) Absorption spectra of Cu-Pc thin films deposited at substrate heating temperature of 100
◦
