Effects of Solvents in the Fabrication of a Hybrid Optical Device Based on GaN and MEH-PPV

Effects of Solvents in the Fabrication of a Hybrid Optical Device Based on GaN and MEH-PPV

Min Jeong Shin · Hyung Soo Ahn · Sam Nyung Yi ^∗

Department of Applied Science, Korea Maritime and Ocean University, Busan 606-791, Korea (Received 17 September 2014 : revised 13 November 2014 : accepted 17 November 2014)

We fabricated an organic/inorganic hybrid structure by using GaN, MEH-PPV (poly(2-methoxy-5(20-ethyl-hexyloxy)-1,4-phenylenevinylene)) and PEDOT:PSS poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) and investigated the effects of solutions of MEH-PPV fiber in different solvents such as chlorobenzene, toluene, THF (tetrahydrofuran), and chloroform. The layer thickness and the luminescence properties of the MEH-PPV solutions with different solvents were affected by the structure of the aromatic or the nonaromatic compound.

Among the solutions, the one with MEH-PPV dissolved in the aromatic compound chlorobenzene showed the lowest threshold voltage, series resistance, and ideality factor. The properties of devices were evaluated by using cross-sectional field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), current-voltage (I-V), and fourier-transform infrared (FT-IR) measurements.

PACS numbers: 72.80.Ey, 72.80.Le

Keywords: GaN, MEH-PPV, Hybrid devices

GaN Ñ ÷ MEH-PPVõ u § T “ Ó Þ” X ¢ hybrid ° Ë Ñ} º  < gX c l S 

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,

>

* > + ä  · ¼ ÿ ›0 ï F¬ £ · T „ ‘ ž$ ß  ^∗

ô

 Dz D G K € ª œ@ /† < Ɠ § 6 £ x6   x õ † < Æõ ,  Òí ß – 606-791

(2014¸   9 Z 4 17{ 9  ~ à Î6 £ §, 2014¸   11 Z 4 13{ 9  à º& ñ ‘ : r ~ à Î6 £ §, 2014¸   11 Z 4 17{ 9  > F  S X ‰& ñ )

‘ :

r ƒ  ½ ¨\ " f  H GaN ü < MEH-PPV x 9  PEDOT:PSS\  ¦ s 6   x # Œ Ä »/Á ºl  s Ú Ôo × ¼ ™ è \  ¦ ] j Œ •

“ ¦, MEH-PPV\  ¦ 9 þ t – Ж Ð $ ™H $ ™, d  ¦ À Ò ' p, THF, Õ ªo “ ¦ 9 þ t – Ж П í2 £ § \  y Œ •y Œ • 6   x K  # Œ 6   x B  7 á x À Ó\   

 É

r s Ú Ôo × ¼ ™ è _  : £ ¤$ í `  ¦ ¶ ú ˜( R˜ Ѐ Œ ¤ . 6   x K   ) a MEH-PPV _  : £ ¤$ í “ É r 6   x B _  ~ ½ ӆ ¾ Ó7 á ¤ <  ʓ É r q  ~ ½ ӆ ¾ Ó 7

á

¤ ½ ¨› ¸\  % ò † ¾ Ó`  ¦ ~ à Î  7 £ x ‚ Ã Ì ¿ ºa  x 9  µ 1 Ï F  g : £ ¤$ í \  % ò † ¾ Ó`  ¦ Å Ò% 3 “ ¦, Õ ª ×  æ ~ ½ ӆ ¾ Ó7 á ¤ 6   x B “   9 þ t – Ж Ð $ ™H $ ™\  6

 

x K ô  Ç MEH-PPV\  ¦  6   x # Œ ] j Œ •ô  Ç s Ú Ôo × ¼ ½ ¨› ¸\ " f ë  H) 3 „  · ú šõ  series resistance x 9  s  © œ>  Ã

º — ¸¿ º  © œ ± ú “ É r ° ú כ_  „  À Ó-„  · ú š : £ ¤$ í `  ¦ f ” `  ¦ S X ‰ “   % i  . ™ è _  : £ ¤$ í “ É r é ß –€   FE-SEM, PL,

„

 À Ó-„  · ú š 8 £ ¤& ñ x 9  FT-IR ì  rF  gZ O `  ¦ s 6   x # Œ › ¸ ÷ &% 3  .

PACS numbers: 72.80.Ey, 72.80.Le

Keywords: GaN, MEH-PPV, s Ú Ôo × ¼ ™ è 

∗

E-mail: [email protected] 14

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License

(http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any

medium, provided the original work is properly cited.

I. " e  ] Ø

þ

j   H Á ºl Ó ü t õ  Ä »l Ó ü t`  ¦ † < Êa   6   x † < ÊÜ ¼– Ð+ ‹ † ¾ Ó © œ  ) a : £ ¤

$ í

`  ¦ t   H s Ú Ôo × ¼ ™ è \  ¦ ] j Œ • “ ¦    H ƒ  ½ ¨

 µ 1 Ï F  g  s š ¸× ¼, I € ª œ„  t , G ' p" f, B j— ¸o  1 p x  € ª œô  Ç ì  r



\ " f Å Ò3 l q`  ¦ ~ à Γ ¦ e ”   [1–6].

Á

ºl Ó ü t ì ø ͕ ¸^ ‰  H a % ~“ É r „  l & h  : £ ¤$ í õ  Z  }“ É r 1 l x  Œ • : £ ¤$ í _

  © œ& h `  ¦ t “ ¦ e ” # Q" f, silicon (Si), germanium (Ge)1 p x _

 c7 á ¤ ì ø ͕ ¸^ ‰ x 9  gallium nitride (GaN), gallium ar- senide (GaAs), zinc oxide (ZnO), cadmium sulfide (CdS) 1

p

x _  III-V7 á ¤ <  ʓ É r II-VI7 á ¤ _   o½ + ËÓ ü t ì ø ͕ ¸^ ‰ 1 p x`  ¦ s 6   x 

#

Œ  Ö ¸ µ 1 Ïy  ƒ  ½ ¨÷ &“ ¦ e ”   [7–12]. Õ ª ×  æ GaN  H 3.4 eV _

  ½ ™× ¼Ì “ s`  ¦ t   H f ” ] X …  ;s + þ A ì ø ͕ ¸^ ‰– Ð" f   É r ì ø ͕ ¸

^

‰ ™ è \  q K  Z  }“ É r “ ¦“ : r \ " f• ¸ ™ è _  : £ ¤$ í `  ¦ Ä »t  † < Ê Ü

¼– Ð" f ' õ AÒ  o <  ʓ É r  ü @‚   % ò % i _  F  g ™ è ÷  r ë ß –  m   “ ¦

“

: r, “ ¦Ø  ¦§ 4 _  „   ™ è \ • ¸ ´ ú §“ É r ƒ  ½ ¨ x 9  & h 6   x s  ÷ &“ ¦ e ” 



 [9,13–15].

¢

¸ô  Ç Ä »l Ó ü t ì ø ͕ ¸^ ‰  H $ q 6   x, ] j› ¸ / B N& ñ _  ç ß –é ß –

†

< Ê, @ /€  & h  o_  6   x s † < Ê,  € ª œô  Ç l ó ø Í_   6   x 0 p x

†

< Ê 1 p x _  s & h s  e ” # Q" f ‰ & ³F , N,N÷-diphenyl-N,N÷- bis(1-naphthyl)-1,1÷biphenyl-4,4diamine (α-NPD), N,N

÷-di(naphth-2-yl)-N,N÷-diphenyl-benzidine (NPB), N’- Bis[3-methylphenyl]-N,N’-diphenylbenzidine (TPD) 1 p x _

 é ß –ì  r   x 9  poly(2-methoxy-5(20-ethyl-hexyloxy)- 1,4-phenylenevinylene) (MEH-PPV), poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PE- DOT:PSS), poly(3-hexylthiophene) (P3HT) ü < ° ú  

“ É

r e  ¦ o  Q\  ¦  6   x # Œ ƒ  ½ ¨ s À Ò# Qt “ ¦ e ”   [16–22]. Õ ª ×  æ MEH-PPV  H / B NÓ  o “ ¦ì  r  “   PPV (poly[phenylenevinylene]) _  Ä »• ¸^ ‰– Ð+ ‹, a % ~“ É r F  g„  • ¸$ í õ

 µ 1 Ï F  g ´ òÖ  ¦ _  : £ ¤$ í `  ¦ t “ ¦ e ” # Q µ 1 Ï F  g  s š ¸× ¼, I € ª œ

„

 t , G ' p" f 1 p x  € ª œô  Ç F  g ™ è \  & h 6   x ) a   [20,23]. ¢ ¸ô  Ç q

“ §& h  Z  }“ É r „  • ¸$ í õ  È Òõ • ¸, î ß –& ñ $ í 1 p x _   © œ& h `  ¦ t 



 H PEDOT:PSS  H Ä »l Ó ü t`  ¦ s 6   x ô  Ç ™ è  ] j Œ • r  „    x 9

 & ñ / B N î  r5 Å x8 £ x s 
 S X ‰ í ß –8 £ x 1 p x _  % i ½ + ɖ РŠҖ Ð  6   x ) a   [21,24]. t ë ß – s  Qô  Ç Ä »l Ó ü t`  ¦ s 6   x # Œ ™ è \  ¦ ] j Œ •

½

+ É r  Ä »l Ó ü t _  7 á x À Ó, 0 l x • ¸, ¿ ºa , 6   x B  1 p x \     B Ä º



 y Œ ™ >  ì ø Í6 £ x # Œ ™ è  ] j Œ •\  e ” # Q" f ´ ú §“ É r # Q 9¹ ¡ § s 

”

> r F  “ ¦ e ”   [1,25–27].

‘

: r ƒ  ½ ¨\ " f  H GaN ü < MEH-PPV x 9  PEDOT:PSS\  ¦ s

6   x # Œ s Ú Ôo × ¼ ™ è \  ¦ ] j Œ • % i Ü ¼ 9, s M : ™ è  ]

j Œ •\  % ò † ¾ Ó`  ¦ p u   H # Œ Q כ ¹“   ×  æ MEH-PPV \  # Œ Q 7

á

x À Ó_  6   x B \  ¦ & h 6   x K  4 Ÿ § Ü ¼– Ð+ ‹ y Œ •y Œ •_   â Ä º ™ è _  :

£ ¤$ í \  p u   H % ò † ¾ Ó`  ¦ › ¸  # Œ ˜ Ѐ Œ ¤ .

II. ÷ m Ç] M ö U ê s0 n É

MOCVD\  ¦ s 6   x # Œ   s # Q l ó ø Í 0 A\  $ “ : r GaN

!

Q( 8 £ x`  ¦ $ í  © œr †   + ' Sis  • ¸i ç  ) a n-GaN \ x 8 £ x`  ¦ 2 µm $ í  © œr (   . $ í  © œ  ) a GaN \ x 8 £ x“ É r  [ j— : r õ  B jò ø Í`  ¦

\

 y Œ •y Œ • 5ì  r ç ß – œ í6 £ §   [ j' ‘ `  ¦ ô  Ç Ê ê ï ß –À Ó Ã ºì  r`  ¦ ] j 

l  0 AK  90 ^◦ C \ " f 10ì  r ç ß – \ P % ƒo  % i  . MEH-PPV



 H 9 þ t – Ж Ð $ ™H $ ™ (chlorobenzene), d  ¦ À Ò ' p (toluene), THF (tetrahydrofuran), 9 þ t – Ж П í2 £ § (chloroform) 6   xÓ  o\  0.6 wt% – Ð y Œ •y Œ • 6   x K  # Œ 30 ^◦ C \ " f 12r ç ß –1 l x î ß – “ §ì ø Í % i 



. Ø  æì  r y  “ §ì ø Í  ) a MEH-PPV 6   xÓ  o`  ¦ GaN \ x 8 £ x 0 A

\

 900 rpm_  5 Å q • ¸– Ð 40œ íç ß –  ïh Aô  Ç Ê ê ï ß –# Œ 6   x B \  ¦ \ O  E

l  0 AK  90 ^◦ C \ " f 10ì  r ç ß – \ P % ƒo \  ¦ z  ´r  % i  . € ª œ /

B

N Å Ò{ 9 8 £ x x 9  S X ‰ í ß –8 £ x % i ½ + É`  ¦ à º' Ÿ  l  0 Aô  Ç 6   xÓ  o  © œI  _

 PEDOT:PSS\  ¦ 3000 rpm \ " f 50œ íç ß – Û ¼— 2 ; ïh A ô  Ç + ' 120 ^◦ C \ " f 15ì  r ç ß – \ P % ƒo \  ¦ z  ´r  % i  . s Ê ê „  F G + þ A

$ í

`  ¦ 0 AK  Ä »l Ó ü t _  { 9  Òì  r`  ¦ ] j ô  Ç + ' e-beam 7 £ x ‚ à Ìl 

\

 ¦ s 6   x # Œ 80 nm_  Au „  F G`  ¦ ‚  × þ ˜& h Ü ¼– Ð 7 £ x ‚ Ã Ì % i 



. XRD (X-ray diffraction) J ‡  `  ¦ s 6   x # Œ GaN \ x  8

£

x _    & ñ $ í `  ¦ › ¸  % i “ ¦, é ß –€   FE-SEM (field emis- sion scanning electron microscopy) õ  PL (photolumi- nescence), „  À Ó-„  · ú š (current-voltage) 8 £ ¤& ñ x 9  FT-IR (fourier transform infrared) ì  rF  gZ O `  ¦ s 6   x # Œ MEH- PPV\  ¦ s 6   x ô  Ç s Ú Ôo × ¼ F  g ™ è  ] j Œ • r  6   x B  p u 



 H % ò † ¾ Ó`  ¦ › ¸  % i  .

III. ÷ m Ç] M ö + s ÇÊ Ý õ m Í À X Ø8 ý

Figure 1“ É r GaN \ x 8 £ x _  XRD J ‡  õ  (0002)\  @ / ô

 Ç ω-rocking curve\  ¦
 ? /% 3  . XRD J ‡  “ É r 2θ = 34.56 ü < 72.88 ^◦ \ " f x ß ¼\  ¦ S X ‰ “   % i Ü ¼ 9, s   H GaN _

 (0002)ü < (0004) €  \  y Œ •y Œ • K { © œô  Ç .   " f GaN

\

x 8 £ x s  [0001] ~ ½ ӆ ¾ ÓÜ ¼– Ð $ í  © œ % i 6 £ §`  ¦ · ú ˜ à º e ”  . ¢ ¸ ô

 Ç (0002)\  @ /ô  Ç ω-rocking curve 8 £ ¤& ñ   õ , FWHMs  0.081 ^◦ _  ° ú כ`  ¦ f ” Ü ¼– Ð" f a % ~“ É r   & ñ $ í `  ¦ t   H GaN

\

x 8 £ x s  $ í  © œ÷ &% 3 6 £ §`  ¦ · ú ˜ à º e ”  .

ô

 Ǽ # , Û ¼— 2 ;  ïh A`  ¦ : Ÿ x ô  Ç e  ¦ o  Q_  ¿ ºa  ] j# Q  H 6   x B _  7

á

x À Ó,  ïh A 5 Å q • ¸, e  ¦ o  Q_  ì  r  | ¾ Ó, 6   xÓ  o_  0 l x • ¸_     o 1

p

x`  ¦ : Ÿ x K  0 p x  9, ¢ ¸ô  Ç e  ¦ o  Q 6   xÓ  o_    ½ + Ë & ñ • ¸  H 6   x B

, e  ¦ o  Q_  € ª œ, 6   xÓ  o_  “ : r • ¸_     o\  % ò † ¾ Ó`  ¦ ~ à Î6 £ § s 

· ú

˜ 94 R e ”   [1,28–34]. Shi 1 p x“ É r MEH-PPV 6   xÓ  o`  ¦ š ¸¤ è n

9 þ t – Ж Ð $ ™H $ ™ (1,2-dichlorobenzene)õ  THF\  ¦ 6   x B – Ð   6

 

x # Œ ] j Œ •ô  Ç Ê ê ° ú  “ É r › ¸| Ü ¼– Ð  ïh A % i `  ¦ M : 6   x B  7 á x À

Ó_  s \  _ K  y Œ •y Œ •   É r ¿ ºa \  ¦ ° ú   H MEH-PPV 8 £ x

Table 1. The structures and properties of chlorobenzene, toluene, THF, and chloroform.

Solvent Formula Structure Molar mass Density Melting point Boiling point Dielectric (g/mol) (g/cm

³

) (

^◦

C) (

^◦

C) Constant

Chlorobenzene C

6

H

5

Cl 112.56 1.11 -45 131 5.602

Toluene C

7

H

8

92.14 0.87 -95 111 2.38

THF C

4

H

8

O 72.11 0.8892 -108.4 66 7.6

Chloroform CHCl

3

119.38 1.489 -63.5 61.15 4.81

(25

^◦

C)

Fig. 1. XRD pattern of GaN epilayer and ω-rocking curves for (0002) reflection of GaN epilayer (inset).

`

 ¦ S X ‰ “   % i   [35]. Table 1\  ‘ : r ƒ  ½ ¨\ " f  6   x ô  Ç 6   x B 

“

  9 þ t – Ж Ð $ ™H $ ™, d  ¦ À Ò ' p, THF, Õ ªo “ ¦ 9 þ t – Ж П í2 £ § _  ½ ¨› ¸ ü

< : £ ¤$ í \  @ /K 
 ? /% 3  . Figure 2  H GaN \ x 8 £ x 0 A

\

   É r 7 á x À Ó_  6   x B \  ¦  6   x # Œ ] j Œ •ô  Ç MEH-PPV 8 £ x _

 FE-SEM é ß –€   s p t s  . MEH-PPV\  ¦ 6   x K  l  0 A ô

 Ç 6   x B _  7 á x À Ó 9 þ t – Ж Ð $ ™H $ ™, d  ¦ À Ò ' p, THF, Õ ªo “ ¦ 9 þ t

–

Ж П í2 £ §{ 9  M : €  • 37.62, 56.43, 282.14, 94.05 nm_  ¿ ºa 

\

 ¦ y Œ •y Œ • f ” `  ¦ S X ‰ “   % i  . s – РÒ'  MEH-PPV 8 £ x _ 

¿

ºa  ~ ½ ӆ ¾ Ó7 á ¤ 6   x B “   9 þ t – Ж Ð $ ™H $ ™õ  d  ¦ À Ò ' p\  6   x K  # Œ ]

j Œ • % i `  ¦ M : ˜ Ð  ~ ½ ӆ ¾ Ó7 á ¤ 6   x B      THFü < 9 þ t – Ж Ð

Ÿ

í2 £ § \  6   x K  % i `  ¦ M :  8 ¿ º,  >  7 £ x ‚ Ã Ì H † d`  ¦ ^  ¦ à º e ”  . ~ ½ Ó

† ¾

Ó7 á ¤ 6   x B   H e  ¦ o  Q chain_  ~ ½ ӆ ¾ Ó7 á ¤ backbone õ  Ä º‚  & h  Ü

¼– Ð  © œ  ñ Œ •6   x`  ¦ ô  Ç .   " f chain[ þ t“ É r 6   x B  ? /\ " f é ß – é

ß – “ ¦ \ P  2 ; + þ AI  ÷ & 9, s  backbone“ É r \ P o “ ¦ S X ‰  © œ H † d Ü

¼– Ð+ ‹, 
_  chain\ " f_  π-„   [ þ t s  s Ö  © ô  Ç chain_  π-„   [ þ t õ  ~ 1 >    5 g”   . 7 £ x    H 0 l x • ¸  H  © œ  ñ Œ •6   x

Fig. 2. Cross-sectional FE-SEM images of MEH-PPV layer prepared from (a) chlorobenzene, (b) toluene, (c) THF, and (d) chloroform on GaN epilayer, respectively.

s

 0 p x ô  Ç ´ ú §“ É r  Òì  r[ þ t`  ¦ ] j/ B N “ ¦,   õ & h Ü ¼– Ð   ½ + Ë_ 

&

ñ • ¸\  ¦ 7 £ x r †    [30,31]. ì ø ̀   q ~ ½ ӆ ¾ Ó7 á ¤ 6   x B   H e  ¦ o  Q_  side group[ þ t õ  Ä º‚  & h Ü ¼– Ð  © œ  ñ Œ •6   x`  ¦ # Œ, e  ¦ o  Q chain“ É r 6   x B -side group  © œ  ñ Œ •6   x`  ¦ þ j@ / o l  0 AK  é

ß –é ß –y  Ñ ü t  Q “ ¦, 6   x B \  @ /ô  Ç ~ ½ ӆ ¾ Ó7 á ¤ backbone _  ” ¸Ø  ¦

`

 ¦ þ j™ è oô  Ç . q ~ ½ ӆ ¾ Ó7 á ¤ 6   x B \ " f MEH-PPV chain“ É r

¢ -

a„  y  Ñ ü t  Q s t  · ú §“ ¦ # QÖ ¼ & ñ • ¸  H Y > Y > _  chain\ " f µ

1 ÏÒ  oé ß – (chromophore)[ þ t  s _  π-„     © œ  ñ Œ •6   x`  ¦ ) ‡ 6

 

x # Œ,   ½ + ˓ É r { 9 # Q± ú ˜ à º e ” t ë ß –, Ø  æì  r ô  Ç 0 l x • ¸\ " f “   ] X

ô  Ç e  ¦ o  Q\  ¦ " f– Ð Ñ ü t  Q >  # Œ Ø  æì  r y    H] X ô  Ç  o  s

 © œ\ " fë ß – π-„    x 9 • ¸ / B N Ä »  ) a   [30,31].   " f ~ ½ Ó

†

¾ Ó7 á ¤ 6   x B \  ¦  6   x   H  â Ä º, 6   x B  ? /_  MEH-PPV_  ì  r



ç ß –   ½ + Ës  “ ¦Ø Ô>  ì  r í ß –÷ &# Q e ” Ü ¼Ù ¼– Ð Û ¼— 2 ;  ïh A r  · û ª

“ É

r } Œ •s  + þ A$ í ÷ &  H ì ø ̀  , q ~ ½ ӆ ¾ Ó7 á ¤ 6   x B \  ¦  6   x ½ + É  â Ä º

Fig. 3. (Color online) Normalized PL spectra of MEH- PPV layer prepared from various solvents on glass. Inset image is molecule structure of MEH-PPV.

MEH-PPV ì  r  ç ß –_    ½ + Ës  Ô  ¦ç  H{ 9  # Œ Û ¼— 2 ;  ïh A Ê ê

\

• ¸ ¿ º î  r MEH-PPV 8 £ x`  ¦ + þ A$ í % i `  ¦  כ s   Ò q ty Œ •  ) a



.

Figure 3“ É r MEH-PPV\  ¦ y Œ •y Œ • 9 þ t – Ж Ð $ ™H $ ™, d  ¦ À Ò ' p, THF, 9 þ t – Ж П í2 £ § \  6   x K  # Œ Ä »o l ó ø Í 0 A\  • ¸Ÿ íô  Ç MEH-PPV 8 £ x _  PL Û ¼& 7 ˜à Ô! 3 s  9, ¶ ú š{ 9  Õ ªa Ë >\  MEH- PPV _  ì  r   — ¸d ” • ¸\  ¦
 ? /% 3  . MEH-PPV  H ~ ½ ӆ ¾ Ó7 á ¤ _

 backboneõ  alkoxy side chainÜ ¼– Ð ½ ¨$ í ÷ &# Q”   µ 1 Ï F  ge  ¦ o

 Qs  . 6   x B  9 þ t – Ж Ð $ ™H $ ™, d  ¦ À Ò ' p, THF, 9 þ t – Ж П í2 £ § { 9

 M : €  • 570, 566, 578, 599 nm_  B j“   x ß ¼\  ¦ y Œ •y Œ • S X ‰ “  

½

+ É Ã º e ”  . s  x ß ¼[ þ t“ É r MEH-PPV _  PPV backbone\ 

"

f # Œl   ) a π-„   [ þ t s  ground state– Ð relaxation÷ &€  " f Ò q

t$ í ÷ &  H  כ Ü ¼– Ð · ú ˜ 94 R e ” Ü ¼ 9, # QL :\  ” > r F    H €  • 635 nm Šҁ  _  x ß ¼  H interchain state \  _ ô  Ç  כ s   [33,36, 37]. s M : MEH-PPV 8 £ x _  B j“   x ß ¼ 0 Au  ~ ½ ӆ ¾ Ó7 á ¤ 6   x B

“   9 þ t – Ж Ð $ ™H $ ™õ  d  ¦ À Ò ' p\  6   x K ô  Ç r « Ñ ˜ Ð  ~ ½ ӆ ¾ Ó7 á ¤ 6

 

x B      THFü < 9 þ t – Ж П í2 £ § \  6   x K ô  Ç Ò  re  ¦ \ " f x  ß

¼  © œ  © œ s 1 l x † < Ê`  ¦ ^  ¦ à º e ”  . s  Qô  Ç 6   x B \  _ ô  Ç x

ß ¼_   © œ  © œ s 1 l x“ É r Nguyen 1 p x _  z  ´+ « >\ " f• ¸ › ' a ¹ 1 Ï÷ &

#

Qt “ ¦ e ”   [30,31]. s  Qô  Ç e  ¦ o  Q µ 1 ÏÒ  oé ß –_  µ 1 Ï F  g Û ¼& 7 ˜ à

Ô! 3 “ É r 6   x B _  F G$ í s  7 £ x ½ + Éà º2 Ÿ ¤ x ß ¼  © œ  © œ s 1 l x

`

 ¦ ô  Ç “ ¦ { 9 ì ø Í& h Ü ¼– Ð · ú ˜ 94 Re ”   [33]. t ë ß – 6   xÓ  o_ 

Fig. 4. (Color online) I-V curve of hybrid structures with various solvents of MEH-PPV. Inset images are semi-logarithmic plot of I-V curve as a function of bias voltage, schematic diagram of hybrid device and optical micrograph top view of the sample.

7 á

x À Ó x 9  0 l x • ¸, ¿ ºa , “ : r • ¸ 1 p x _   € ª œô  Ç   à º\  _ K  e  ¦ o  Q_    ½ + Ë U  ´s  x 9  \  -t  „  s \     o Ò q t  x ß ¼  H  © œ 

 © œ ÷  r ë ß –  m   é ß –  © œÜ ¼– Ð_  s 1 l x • ¸ { 9 # Qè ß – “ ¦ ˜ Ð

“

¦÷ &# Qt “ ¦ e ”   [31–35].

Figure 4  H MEH-PPV _  6   x B  7 á x À Ó\    É r s Ú Ôo 

×

¼ ½ ¨› ¸_  „  À Ó-„  · ú š : £ ¤$ í `  ¦
  · p . — ¸Ž  H s Ú Ôo × ¼

½

¨› ¸\ " f  s š ¸× ¼_  & ñ À Ó: £ ¤$ í `  ¦ S X ‰ “  ½ + É Ã º e ” % 3 “ ¦, Õ ª

×

 æ 9 þ t – Ж Ð $ ™H $ ™`  ¦  6   x ô  Ç ½ ¨› ¸\ " f €  • 0.8 V_  ë  H) 3  „  · ú š õ

 83.5 Ω_  series resistance\  ¦
 ? /% 3  . y Œ • ½ ¨› ¸[ þ t  î

 r X < 9 þ t – Ж Ð $ ™H $ ™`  ¦  6   x K  ] j Œ •  ) a ½ ¨› ¸_   â Ä º   É r 6   x B

\  ¦ s 6   x K  ï  r q   ) a ½ ¨› ¸\  q K  † ¾ Ó © œ  ) a : £ ¤$ í `  ¦ ˜ Ðs   H X

<, s   H ç  H{ 9  >  ì  r í ß –  ) a MEH-PPV 8 £ x _  ¿ ºa _  s 

 „  À Ó-„  · ú š : £ ¤$ í \  ß ¼>  % ò † ¾ Ó`  ¦ Å Ò% 3 `  ¦  כ s   Ò q ty Œ •  ) a



. s  Qô  Ç MEH-PPV_  6   x B  x 9  8 £ x _  ¿ ºa _  s  ™ è



_  : £ ¤$ í \  % ò † ¾ Ó`  ¦ p u   H ƒ  ½ ¨   õ   H Y. Shi 1 p x \  _  K

" f• ¸ S X ‰ “   ½ + É Ã º e ”   [35].   " f ‘ : r ƒ  ½ ¨\ " f ] j Œ • ô

 Ç GaNü < MEH-PPV Ä »/Á ºl  s Ú Ôo × ¼ ½ ¨› ¸\ " f  H 9

þ

t – Ж Ð $ ™H $ ™`  ¦ s 6   x # Œ €  • 37.62 nm ¿ ºa _  MEH-PPV 8

£

x`  ¦ ] j Œ • % i `  ¦ r   © œ † ¾ Ó © œ  ) a  s š ¸× ¼ : £ ¤$ í `  ¦
 



· p “ ¦ Ò q ty Œ •  ) a  .

¢

¸ô  Ç y Œ • ½ ¨› ¸_  „  À Ó-„  · ú š : £ ¤$ í “ É r \ P „    ~ ½ ÓØ  ¦ s  : r \  l

œ í # Œ ì  r$ 3  0 p x  .

I = I s

 exp qV

nk _B T − 1



(V  k B T /q)

#

Œl " f I ^s   H Ÿ í o„  À Ó, q  H „    ô  Ç > h_  „   | ¾ Ó, V   H   s

š ¸× ¼\  “    ) a „  · ú š, n“ É r s  © œ> à º (ideality factor), k _B   H Boltzmann  © œÃ º, T   H ] X @ /“ : r • ¸\  ¦
  · p . ¶ ú š{ 9  Õ

ªa Ë >\  „  À Ó-„  · ú š Õ ªA á Ô\  ¦ semi-logarithmic   ¨ 8 Š # Œ

Table 2. IR absorption band assignments for MEH-PPV solution by chlorobenzene, GaN epilayer, and MEH-PPV layer prepared from chlorobenzene on GaN epilayer [cm ⁻¹ ].

MEH-PPV GaN MEH-PPV on Assignment [ref. 47-49]

Solution epilayer GaN epilayer

2957.17 2956.36 2952-2958 CH

3

asymmetric C-H stretch

2927.05 2926.76 2921-2926 CH

2

asymmetric C-H stretch

2871.50 2870.60 2870 CH

2

symmetric C-H stretch

2858.49 2858.59 2859-2867 CH

3

symmetric C-H stretch

1747.03 1733.35 1730 Ga-H local vibrational mode

1504.37 1504.29 1502-1518 C-C ring semi-circular stretch

1463.35 1463.45 1465 (R-O)-CH

2

asymmetric deformation

1412.93 1412.50 1406-1423 C-C ring semi-circular stretch

1380.83 1380.91 1377-1388 C-C ring stretch

1352.68 1352.01 1356-1359 -O-CH

3

wag and CH

3

symmetric deformation 1312.81 1313.16 1300 wagging local vibrational modes of CH

2

in GaN 1280.58 1280.48 1274 wagging local vibrational modes of CH

2

in GaN

1254.56 1254.87 1257 phenylene-(O-CH-) stretch

1204.53 1204.04 1205-1208 (phenylene-O)-C stretch

1040.35 1040.08 1046-1047 phenylene-alkoxy stretch

968.34 970.43 962-969 phenylene ring breathing

737.87 738.52 735 A

1

(LO) phonon mode in GaN

526.07 526.00 533 A

1

(TO) phonon mode in GaN

508.57 508.35 518/517 Sapphire

478.67 479.69 488 Sapphire

Fig. 5. (Color online) FT-IR spectra of MEH-PPV in chlorobenzene, GaN epilayer, and MEH-PPV layer pre- pared from chlorobenzene on GaN epilyaer.

 ? /% 3 “ ¦, Õ ªA á Ô_  l Ö  ¦ l – РÒ'  s  © œ > à º x 9  ™ è  _

 F   ½ + Ë B j& m 7 £ §`  ¦ 0 p u ½ + É Ã º e ”  . s  © œ& h “    s š ¸

×

¼{ 9   â Ä º, Õ ªA á Ô_  l Ö  ¦ l – РÒ'  % 3 # Qt   H s  © œ> à º

 n = 1s €   ”  $ í % ò % i \ " f H o # Q_  F   ½ + Ës  { 9 # Q
 9, s  © œ > à º n < 2“    â Ä º / B N ç ß –„   % ò % i \ " f F   ½ + Ë

„

 À Ó ” > r F ô  Ç . ì ø ̀   n > 2_  s  © œ > à º  H ™ è  ? /\  '

V , a A „  À Ó ” > r F † < Ê`  ¦ _ p ô  Ç  [38]. 6   x B  9 þ t – Ж Ð

 $

™H $ ™, d  ¦ À Ò ' p, THF, 9 þ t – Ж П í2 £ §{ 9  M : €  • n = 2.2, 14.8, 10.6, 12.0 _  s  © œ> à º\  ¦ % 3 `  ¦ à º e ” % 3  . s  Qô  Ç  H s  © œ

>

à º  H Ä »/Á ºl Ó ü t`  ¦ s 6   x ô  Ç s Ú Ôo × ¼ ™ è \ " f H o 

#

Q_  ' V , a A x 9  ] X 8 ú ¤ $ † ½ Ó, ¿ º Ó ü t| 9 _  > €  \  ” > r F    H   

†

< Ê\  _ K  n = 5.3\ " f 29.3 t _   H ° ú כs  ˜ Г ¦  ) a   e ”  Ü

¼ 9 [26,39–41], GaN l ì ø Í_   s š ¸× ¼\ " f  H n = 2.0 \ 

"

f 7.0  s _  H o # Q_  ' V , a A\  _ ô  Ç s  © œ> à º ˜ Г ¦

÷

&% 3   [42–46].   " f  € ª œô  Ç 6   x B \    É r s Ú Ôo × ¼

½

¨› ¸ ×  æ 9 þ t – Ж Ð $ ™H $ ™`  ¦  6   x # Œ ] j Œ •ô  Ç ™ è   © œ  Œ •

“ É

r ° ú כ_  s  © œ> à º\  ¦
 ? /Ù ¼– Ð+ ‹, 7 £ ¤ ™ è _  ' V , a A „   À

Ó\  ¦ y Œ ™™ èr &  ™ è _  „  À Ó-„  · ú š : £ ¤$ í `  ¦ † ¾ Ó © œr (   “ ¦ Ò q

ty Œ •ô  Ç .

Figure 5  H 9 þ t – Ж Ð $ ™H $ ™\  6   x K ô  Ç MEH-PPV 6   xÓ  oõ  MEH-PPV  7 £ x ‚ Ã Ì  ) a GaN \ x 8 £ x, Õ ªo “ ¦ GaN \ x 8 £ x y

Œ

•y Œ •\  @ /K  FT-IR ì  rF  gZ O `  ¦ s 6   x # Œ 8 £ ¤& ñ  ) a È Òõ  Û ¼& 7 ˜ à

Ô! 3 _    õ s  . Û ¼& 7 ˜à Ô! 3 \ 
 è ß – y Œ •y Œ •_  x ß ¼_  0 A u

 x 9  " é ¶ “  \  @ /K  Table 2\  כ ¹€  • & ñ o  % i   [47–49].

MEH-PPV  7 £ x ‚ Ã Ì  ) a GaN \ x 8 £ x _  FT-IR Û ¼& 7 ˜à Ô! 3 “ É r MEH-PPV 6   xÓ  o_  x ß ¼ü < GaN \ x 8 £ x _  x ß ¼[ þ t`  ¦  _ 



 Ÿ í† < ʽ + É ÷  r ë ß –  m   MEH-PPV GaN \ x 8 £ x 0 A\  7

£

x ‚ Ã Ì x 9  \ P % ƒo   ) a s Ê ê\ • ¸ x ß ¼[ þ t _     o  _  \ O Ü ¼ Ù

¼– Ð, / B N& ñ Ê ê\ • ¸ MEH-PPV_   o† < Æ& h  $ í | 9 _     o

{ 9

# Q
t  · ú §€ Œ ¤6 £ §`  ¦ S X ‰ “   ½ + É Ã º e ”  .

IV. + s Ç Â ] Ø

‘

: r  7 Hë  H \ " f  H GaN ü < MEH-PPV x 9  PEDOT:PSS\  ¦ s

6   x # Œ s Ú Ôo × ¼ ™ è \  ¦ ] j Œ • “ ¦, s M : MEH-PPV _

 6   x B _  7 á x À Ó\    É r s Ú Ôo × ¼ ™ è _  : £ ¤$ í `  ¦ ¶ ú ˜( R

˜

Ѐ Œ ¤ . 6   x B _  7 á x À Ӎ  H 9 þ t – Ж Ð $ ™H $ ™, d  ¦ À Ò ' p, THF, Õ ªo 

“

¦ 9 þ t – Ж П í2 £ §`  ¦  6   x % i  . Û ¼— 2 ;  ïh A ~ ½ ÓZ O `  ¦ s 6   x 

#

Œ GaN \ x 8 £ x 0 A\  MEH-PPV 8 £ x`  ¦ ] j Œ • # Œ Õ ª : £ ¤

$ í

`  ¦ ì  r$ 3 ô  Ç   õ , ~ ½ ӆ ¾ Ó7 á ¤ 6   x B “   9 þ t – Ж Ð $ ™H $ ™õ  d  ¦ À Ò ' p

`

 ¦  6   x % i `  ¦ M : ~ ½ ӆ ½ Ó7 á ¤ 6   x B      THFü < 9 þ t – Ж П í 2

£

§`  ¦  6   x % i `  ¦ M :˜ Ð  · û ª“ É r ¿ ºa \  ¦ t “ ¦ 7 £ x ‚ Ã Ì | ¨ c ÷  r ë

ß –  m   ~ ½ ӆ ¾ Ó7 á ¤ 6   x B \  ¦  6   x % i `  ¦ M :˜ Ð  ~ ½ ӆ ¾ Ó7 á ¤ s 



   6   x B \  ¦  6   x % i `  ¦ M : µ 1 Ï F  g x ß ¼_  0 Au   © œ  © œ s

1 l x`  ¦ † < Ê`  ¦ › ' a ¹ 1 Ï % i  . ¢ ¸ô  Ç „  À Ó-„  · ú š 8 £ ¤& ñ   õ , — ¸

Ž

 H Ò  re  ¦ \ " f  s š ¸× ¼_  & ñ À Ó: £ ¤$ í `  ¦ S X ‰ “  ½ + É Ã º e ” % 3 “ ¦, Õ

ª ×  æ 9 þ t – Ж Ð $ ™H $ ™`  ¦  6   x ô  Ç s Ú Ôo × ¼ ½ ¨› ¸\ " f  © œ

± ú

“ É r ë  H) 3 „  · ú šõ  series resistance x 9  s  © œ> à º\  ¦ S X ‰ “   

%

i  . Õ ªo “ ¦ FT-IR`  ¦ : Ÿ x K  ™ è  ] j Œ •`  ¦ 0 Aô  Ç / B N& ñ \ " f MEH-PPV _   o† < Æ& h  $ í | 9 _     o { 9 # Q
t  · ú §6 £ §`  ¦ S X ‰

“

  % i  .

P

c p 8 ý ò k >

s

  7 Hë  H“ É r 2012¸  • ¸ & ñ Â Ò (“ §¹ ¢ ¤ õ † < Æl Õ ü t  Ò)_  F " é ¶ Ü ¼

–

Ð ô  Dz D Gƒ  ½ ¨F é ß –_  l œ íƒ  ½ ¨ \ O  t " é ¶`  ¦ ~ à Î  à º' Ÿ  ) a  כ e ”

 (2012R1A1A2000886).

REFERENCES

[1] M. J. Shin, D.-O. Gwon, G. S. Lee, H. S. Ahn and S. N. Yi et al., J. Lumin. 147, 1 (2014).

[2] I.-A. Lei, D.-F. Lai, T.-M. Don, W.-C. Chen and Y.- Y. Yu et al., Mater. Chem. Phys. 144, 41 (2014).

[3] F. Zhu, X. Chen, L. Zhou, J. Zhou and J. Yang et al., Thin Solid Films 551, 131 (2014).

[4] Y. Wang, K. Liu, P. Mukherjee, D. A. Hines and P.

Santra et al., Phys. Chem. Chem. Phys. 16, 5066 (2014).

[5] N. B. Sonawane, R. R. Ahire, K. V. Gurav, J. H.

Kim and B. R. Sankapal, J. Alloys Compd. 592, 1 (2014).

[6] D. H. Jung, H. M. Jeong and B. K. Kim, J. Mater.

Chem. 20, 3458 (2010).

[7] W. S. Fegadolli, L. Feng, M. M.-U Rahman, J. E.

B. Oliveira and V. R. Almeida et al., Opt. Express 22, 3425 (2014).

[8] Y. G. Yoon, T. K. Kim, I.-C. Hwang, H.-S. Lee and B.-W. Hwang et al., ACS Appl. Mater. Interfaces 6, 3150 (2014).

[9] M. T. Hardy, F. Wu, C. -Y. Huang, Y. Zhao and D.

F. Feezell et al., IEEE Photon. Technol. Lett. 26, 43 (2014).

[10] S. J. MacLeod, A. M. See, Z. K. Keane, P. Scriven and A. P. Micolich et al., Appl. Phys. Lett. 104, 012114 (2014)

[11] R. Mariappan, V. Ponnuswamy, R. Suresh, P.

Suresh and A. C. Bose et al., J. Alloys Compd. 582, 387 (2014).

[12] P. Guo, W. Hu, Q. Zhang, X. Zhuang and X. Zhu et al., Adv. Mater. 26, 2844 (2014).

[13] J. Zhu, H. Zhang, Z. Zhu, Q. Li and G. Jin, Opt.

Commun. 322, 66 (2014).

[14] J. Moreke, M. J. Uren, S. V. Novikov, C. T. Foxon and S. H. Vajargah et al., J. Appl. Phys. 116, 014502 (2014).

[15] M. Iqbal, P. -S. Ko and S. -D. Kim, Curr. Appl.

Phys. 14, 1099 (2014).

[16] A. Sadakata, K. Osada, D. Taguchi, T. Manaka and M. Iwamoto, Thin Solid Films 554, 110 (2014).

[17] C. Xiang, N. Chopra, J. Wang, C. Brown and S. Ho et al., Org. Electron. 15, 1702 (2014).

[18] J.-B. Lee, W.-J. Lee and T.-W. Kim, Trans. Electr.

Electron. Mater. 15, 41 (2014).

[19] K. S. Yook and J. Y. Lee, Adv. Mater. 26, 4218 (2014).

[20] J.-C. Chen, H.-C. Wu, C.-J. Chiang, T. Chen and L. Xing, J. Mater. Chem. C 2, 4835 (2014).

[21] M. Kim, M. J. Shin, D. Gwon, H. S. Ahn and S. N.

Yi et al., Jpn. J. Appl. Phys. 52, 01AD02 (2013).

[22] M. E. Gemayel, A. Narita, L. F. D¨ ossel, R. S. Sun- daram and A. Kiersnowski et al., Nanoscale 6, 6301 (2014).

[23] R. Estevam-Alves, P. H. D. Ferreira, G. F. B.

Almeida, W. S. Sousa and C. R. Mendonc, Appl.

Surf. Sci. 314, 633 (2014).

[24] S. Ahmad, M. Deepa and S. Singh, Langmuir 23,

11430 (2007).

[25] M. Willander, O. Nur, S. Zaman, A. Zainelabdin and N. Bano et al., J. Phys. D: Appl. Phys. 44, 224017 (2011).

[26] S. Ebrahim, M. Soliman and T. M. Abdel-Fattah, J. Electron. Mater. 40, 2033 (2011).

[27] S. Tokito, T. Iijima, T. Tsuzuki and F. Sato, Appl.

Phys. Lett. 83, 2459 (2003).

[28] R. Konenkamp, R. C. Word and C. Schlegel, Appl.

Phys. Lett. 85, 6004 (2004).

[29] M. J. Shin, M. Kim, G. S. Lee, H. S. Ahn and S. N.

Yi et al., Mater. Lett. 91, 191 (2013).

[30] T.-Q. Nguyen, V. Doan and B. J. Schwartz, J.

Chem. Phys. 110, 4068 (1999).

[31] T.-Q. Nguyen, I. B. Martini, J. Liu and B. J.

Schwartz, J. Phys. Chem. B 104, 237 (2000).

[32] I. D. W. Samuel, G. Rumbles, C. J. Collison, S. C.

Moratti and A. B. Holmes, Chem. Phys. 227, 75 (1998).

[33] M. Zheng, F. Bai and D. Zhu, J. Photochem. Pho- tobiol., A 116, 143 (1998).

[34] J. H. Hsu, W. S. Fann, P. H. Tsao, K. R. Chuang and S.-A. Chen, J. Phys. Chem. A 103, 2375 (1999).

[35] Y. Shi, J. Liu and Y. Yang, J. Appl. Phys. 87, 4254 (2000).

[36] C. Ton-That, G. Stockton, M. R Phillips, T.-P.

Nguyen and C. H. Huang et al., Polym. Int. 57, 496 (2008).

[37] R. Traiphol, N. Charoenthai, T. Srikhirin, T. Kerd- charoen and T. Osotchan et al., Polymer 48, 813 (2007).

[38] C. T. Sah, R. N. Noyce and W. Shockley, Proc. IEEE Inst. Electr. Electron. Eng. 45, 1228 (1957).

[39] R. Kumar, N. Khare, G. L. Bhalla and M. N. Ka- malasanan, Thin Solid Films 518, e61 (2010).

[40] K. Dutta and S. K. De, Mater. Lett. 61, 4967 (2007).

[41] J. Sun, B. N. Pal, B. J. Jung and H. E. Katz, Org.

Electron. 10, 1 (2009).

[42] P. Perlin, M. Osi´ nski, P. G. Eliseev, V. A. Smagley and J. Mu, M. Banas et al., Appl. Phys. Lett. 69, 1680 (1996).

[43] J. M. Shah, Y.-L. Li, T. Gessmann and E. F. Schu- bert, J. Appl. Phys. 94, 2627 (2003).

[44] A. Chitnis, A. Kumar, M. Shatalov, V. Adivara- han and A. Lunev et al., Appl. Phys. Lett. 77, 3800 (2000).

[45] Y. Dong, B. Tian, T. J. Kempa and C. M. Lieber, Nano Lett. 9, 2183 (2009).

[46] H. C. Casey, Appl. Phys. Lett. 68, 2867 (1996).

[47] K. F. Voss, C. M. Foster, I. Smilowitz, D. Mihailovic and S. Askari et al., Phys. Rev. B 43, 5109 (1991).

[48] W. H. Sun, K. M. Chen, Z. J. Yang, J. Li and Y. Z.

Tong et al., J. Appl. Phys. 85, 6430 (1999).

[49] H. Qiu, C. Cao and H. Zhu, Mater. Sci. Eng., B 136,

33 (2007).