Thin films of Poly(3-hexylthiophene-2,5-diyl) (P3HT) were prepared from chloroform, 1,2 dichlorobenzene and toluene solutions by spin coating technique on quartz substrates. The absorption and photoluminescence (PL) measurements were performed on the P3HT films to investigate the influence of solvent on the optical properties of the films. The results shows that the UV-vis absorption of P3HT film spin-coated from toluene is red shifted compared to the spectra of the films spin-coated from either chloroform or 1,2 dichlorobenzene. The surface morphology of P3HT: [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester (Modified Fullerene) thin films spin-coated from different solvents were studied using Atomic Force Microscope (AFM), the thin film spin-coated from 1,2 dichlorobenzene show the smoother surface.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3194

Omer, B.M.

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 5 No 3, 03010(4pp) (2013) Том 5 № 3, 03010(4cc) (2013)   2077-6772/2013/5(3)03010(4) 03010-1  2013 Sumy State University Optical Properties of Poly (3-hexylthiophene-2,5-diyl) and Poly (3-hexylthiophene- 2,5-diyl) / [6,6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester Thin Films   B.M. Omer*  Department of Applied Physics and Mathematics, Faculty of Applied Science and Computer,  Omdurman Ahlia University, P.O. Box 786, Omdurman Sudan   (Received 31 January 2013; revised manuscript received 01 July 2013; published online 12 July 2013)  Thin films of Poly(3-hexylthiophene-2,5-diyl) (P3HT) were prepared from chloroform, 1,2 dichlorobenzene and toluene solutions by spin coating technique on quartz substrates. The absorption and photoluminescence (PL) measurements were performed on the P3HT films to investigate the influence of solvent on the optical properties of the films. The results shows that the UV-vis absorption of P3HT film spin-coated from toluene is red shifted compared to the spectra of the films spin-coated from either chloro-form or 1,2 dichlorobenzene. The surface morphology of P3HT: [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester (Modified Fullerene) thin films spin-coated from different solvents were studied us-ing Atomic Force Microscope (AFM), the thin film spin-coated from 1,2 dichlorobenzene show the smoother surface.  Keywords: Poly (3-hexylthiophene), Modified fullerene, Optical properties, Thin films, AFM.    PACS numbers: 78.66.Qn,78.40.Me                                                              * bushra_omer4@yahoo.com 1. INTRODUCTION   Polymer solar cells have shown a potential to har-ness solar energy in a cost-effective way. The concept of generating specific fullerenes that are compatible with specific polymers has great potential for increasing the performance of bulk heterojunction polymer solar cells through the optimization of the morphology. The nano-morphology of the organic photoactive layer has a strong relationship with the performance of the polymer solar cells [1]. The morphology of this layer can be strongly affected by the processing conditions used such as the donor-acceptor composition [2], the solvent and the thermal annealing of the organic layer [3, 4]. Sever-al studies in the literature discussed the effect of solvent on the optical and surface morphology of Poly (3-hexylthiophene-2,5-diyl) (P3HT): [6, 6]-Phenyl C61-butyric Acid methyl Ester (PCBM) thin films [5, 6]. The design and synthesis of modified fullerene with a higher LUMO energies compared to PCBM is essential to have a higher open circuit voltage and higher efficiency in bulk heterojunction polymer solar cells [7, 8, 9]. To our knowledge there is no published study on the optical and surface morphology of P3HT: [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester (Modified full-erene) thin films. In this paper we report on the effect of preparation conditions on the optical properties of the p-type donor polymer P3HT thin films and on the surface morphology of the thin films of P3HT: [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester.  2. EXPERIMENTS   The p-type donor polymer P3HT and the n-type  acceptor [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester (modified fullerene) in this study were purchased from sigma-Aldrich Corporation and American Dye Source, Inc. respectively; the chemical structures are shown in Fig. 1. All materials were used as received with-out further purification. For the UV-vis absorption and photoluminescence (PL) measurements, P3HT and P3HT: Modified fullerene films were prepared by using spin coat-ing technique. Chloroform, 1,2 dichlorobenzene and tolu-ene were used as solvents; the solutions were spin coated onto quartz substrates. P3HT films were prepared at the concentration of about 11 mg/ml of solvent; the polymer solutions were spin-coated at 2000 rpm. The properties of the films were obtained on a Lambda-900 UV/Vis/NIR spectrophotometer (Perkin Elmer) and on LS55 lumines-cence spectrometer (Perkin Elmer).          a                                        b  Fig. 1 – Chemical structure of (a) poly (3-hexylthiophene-2,5-diyl) and (b) [6,6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester  For surface morphology characterization, P3HT and modified fullerene were dissolved in chloroform, 1,2 dichlorobenzene and toluene to yield a P3HT: modi-fied fullerene (10.22 : 10.92 mg/ml chloroform, 10.41 : 10.38 mg/ml 1,2 dichlorobenzene and 10.50 : 10.56 mg/ml toluene) solutions. The quartz sub-strates were cleaned by ultrasonic treatment for 10 minutes using acetone and isopropyl alcohol sequen-tially. After cleaning of the quartz substrates the solu-tions were spin coated at 2000 rpm for 40 seconds. The surface morphology of P3HT: modified fullerene thin films spin coated from different solvents were character-ized by atomic force microscopy (CP-II veeco).  B.M. OMER J. NANO- ELECTRON. PHYS. 5, 03010 (2013)   03010-2 3. RESULTS AND DISCUSSIONS  The UV-vis absorption spectra of P3HT thin films spin-coated from chloroform, toluene and 1,2 dichlorobenzene solutions were recorded. Fig. 2 shows the UV-vis absorption spectra of the P3HT thin films fabricated from the different solvents. For the ab-sorption spectra of P3HT film fabricated from chloro-form, wavelength of the absorption peak ( max) is at 526 nm and two shoulders appeared at 488 nm and 588 nm. For the P3HT film fabricated from 1,2 dichlorobenzene, max is 556 nm showing a red-shift and clear shoulders appeared at 527 nm and 603 nm. For the P3HT film prepared from toluene, the wavelength of the absorption peak is the same as the one prepared from 1,2 dichlorobenzene at 556 nm and the shoulders ap-peared at 522 nm and 603 nm. The strength of the maxi-mum peak and the shoulder at higher wavelength of the films prepared from 1,2 dichlorobenzene or toluene is in-creased compared with that prepared from chloroform. It was clear that 1,2 dichlorobenzene and toluene promotes a higher degree of ordering in P3HT films than chloroform. The shift in the peak absorption wavelength in the differ-ent solvents may be attributed to an increased interchain interaction among P3HT chains. The absorption band edge of the films using chloroform, 1,2 dichlorobenzene and toluene solvents are observed at 660 nm (1.88 eV), 658 nm (1.89 eV) and 675 nm (1.84 eV), respectively.    Fig. 2 – The UV-vis spectra of pure P3HT film spin-coated from chloroform, 1,2 dichlorobenzene and toluene  The photoluminescence (PL) emission spectra of P3HT was recorded in different solvents and are de-picted in Fig. 3, the photoluminescence spectra do not show significant differences. The PL spectrums exhibit peaks at 643 nm, 649 nm and 650 nm for the films spin-coated from chloroform, 1,2 dichlorobenzene and toluene, respectively. The red shift in energy between the optical absorption and photoluminescence emission peaks is about 117 nm for thin film spin-coated from chloroform, 93 nm for the one spin-coated from 1,2 dichlorobenzene and 94 nm for toluene. Absorption and photoluminescence data for P3HT thin films are summarized in Table 1. Fig. 4 shows the UV-vis  absorption spectrum of [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester thin film. Two peaks appear at 266 and 336 nm and there is abroad tail of absorption extended to as long as 800 nm.   Fig. 3 – The PL spectra of pure P3HT film spin-coated from toluene, 1,2 dichlorobenzene and chloroform    Fig. 4 – The UV-vis absorption of pure Modified Fullerene film spin-coated from chloroform  Fig. 5 display the UV-vis spectra of the P3HT: Modi-fied fullerene (1:1) ratio blended film. The UV-vis ab-sorption bands of the blend film appeared at 266 nm, 337 nm, 553 nm and 603 nm. The peaks 266 nm and 337 nm arise from the modified fullerene; the two other peaks with lower energies are caused by P3HT. We have extracted the onset wavelength of the blend with a linear fit near the absorption edge. The extracted onset wavelength was found to be 661 nm (1.88 eV). As shown in Fig. 6 the absorption of the films with in-creasing amount of Modified fullerene reduced signifi-cantly in the visible range, specifically between 450 nm and 650 nm which is the peak absorption wavelength band for P3HT. The maximum absorption wavelength for all films shows no change. However, in the wave length lower than 400 nm, in the range of the peak ab-sorption of the modified fullerene, the absorption of the films with increasing amount of modified fullerene is enhanced significantly. It has been reported by Vishal Shrotriya et al. [2] that there is a modification in the absorption spectra of P3HT:PCBM composite films with 67 wt % and higher amount of PCBM, the reason is due to the presence of PCBM which destructs the ordering in the P3HT chains. However, the amount of modified fullerene in our study is 50 wt % and less, so it has no effect on the chain ordering of P3HT. The film with the (3:1) P3HT: Modified fullerene shows the highest ab-sorption in the range between 450 nm and 650 nm.  OPTICAL PROPERTIES OF POLY (3-HEXYLTHIOPHENE-2,5-DIYL)… J. NANO- ELECTRON. PHYS. 5, 03010 (2013)   03010-3   Fig. 5 – The UV-vis absorption of P3HT: Modified Fullerene (1:1) film spin-coated from 1, 2 dichlorobenzene     Fig. 6 – The UV-vis absorption spectra for P3HT: Modified fullerene films with different D/A ratio, spin coated from 1,2 diclorobenzene with spin speed of 2000 rpm.Table 1 – Optical data of P3HT in thin films spin-coated from different solvents  Solvent  max,UV (nm) onset, (nm) max,PL (nm) Stokes shift (nm) Eg  (eV) chloroform 526 660 643 117 1.88 1,2 dichlorobenzene 556 658 649 93 1.89 toluene 556 675 650 94 1.84  AFM is a powerful tool to study the nanomorphology of organic blends in thin films. The surface topography usually gives a good insight into the film formation  ability and the tendency of the components to phase se-parate. Fig. 7a displays AFM images of P3HT: Modified fullerene blended film prepared from chloroform; the area roughness is 8.8 nm. We observe phase separation of about 0.2 m. The blended film prepared from 1,2 dichlorobenzene shows a smooth surface with an area roughness of 2.1 nm (see Fig. 7b). We observe a very small-scale phase separation (less than 0.1 m) which is favorable for charge separation, charge transport, or charge collection in polymer solar cells. However, Fig. 7c shows that the blended film prepared from toluene have a rough surface area with area roughness of 22.5 nm and a large-scale phase separation.                                           a                                                          b                                                       c             Fig. 7 – AFM images (5  5 m2) of (1:1) P3HT: Modified fullerene film spin coated from (a) chloroform on quartz substrate (area roughness  8.83 nm and average height  86.67 nm) (b). 1,2dichlorobenzene on quartz substrate (area roughness  2.11 nm and average height  10.42 nm) and (c) toluene on quartz substrate (area roughness  22.49 nm and average height  71.47 nm)  4. CONCLUSIONS  In summary, we have shown that the absorption and photoluminescence of P3HT films are dependent on prep-aration conditions. Further, AFM images were used to study the P3HT: Modified fullerene film morphology spin-coated from different solvents. The results show that the surface morphology of the P3HT: Modified fullerene thin films depend strongly on the preparation solvent.  AKNOWLEDGEMENTS  Author is grateful to the school of Applied physics and the Institute of Microengineering and Nanoelec-tronics (IMEN), University of Kebangsaan Malaysia for unlimited support.       B.M. OMER J. NANO- ELECTRON. PHYS. 5, 03010 (2013)   03010-4  REFERENCES  1. A.J. Moule, K. Meerholz, Adv. Mater. 20, 240 (2008). 2. Vishal Shrotriya, Jianyong Ouyang, Ricky J. Tseng, Gang Li, Yang Yang, Chem. Phys. Lett. 411, 138 (2005). 3. Maher Al-Ibrahim, Oliver Ambacher, Steffi Sensfuss, Gerhard Gobsch, Appl. Phys. Lett. 86, 201120 (2005). 4. Gang Li, Vishal Shrotriya, Yan Yao, Yang Yang, J. Appl. Phys. 98, 043704 (2005). 5. Kenji Kawano, Jun Sakai, Masayuki Yahiro, Chi-haya Adachi, Sol. Energ. Mater. Sol. C. 93, 514 (2009). 6. Yladzimir Zhokhavets, Tobias Erb, Gerhard Gobsch, Ma-her Al-Ibrahim, Oliver Ambacher, Chem. Phys. Lett. 418, 347 (2006). 7. C.J. Brabec, A. Cravino, D. Meissner, N.S. Sariciftci, M.T. Rispens, L. Sanchez, J.C. Hummelen, T. Fromherz, Thin Solid Films 403-404, 368 (2002). 8. Floris B. Kooistra, Joop Knol, Fredrik Kastenberg, Lacra-mioara M. Popescu, Wiljan J.H. Verhees, Jan M. Kroon, Jan C. Hummelen, Org. Lett. 9, 551 (2007). 9. Christoph J. Brabec, Antonio Cravino, Dieter Meissner, N. Serdar Sariciftci, Thomas Fromherz, Minze T. Rispens, Luis Sanchez, Jan C. Hummelen, Adv. Funct. Mater. 11, 374 (2001).   

Optical Properties of Poly (3-hexylthiophene-2,5-diyl) and Poly (3-hexylthiophene-2,5-diyl) / [6,6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester Thin Films

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 5 No 3, 03010(4pp) (2013) Том 5 № 3, 03010(4cc) (2013) 
 
 
2077-6772/2013/5(3)03010(4) 03010-1  2013 Sumy State University 
Optical Properties of Poly (3-hexylthiophene-2,5-diyl) and Poly (3-hexylthiophene- 
2,5-diyl) / [6,6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester Thin Films  
 
B.M. Omer* 
 
Department of Applied Physics and Mathematics, Faculty of Applied Science and Computer,  
Omdurman Ahlia University, P.O. Box 786, Omdurman Sudan  
 
(Received 31 January 2013; revised manuscript received 01 July 2013; published online 12 July 2013) 
 
Thin films of Poly(3-hexylthiophene-2,5-diyl) (P3HT) were prepared from chloroform, 
1,2 dichlorobenzene and toluene solutions by spin coating technique on quartz substrates. The absorption 
and photoluminescence (PL) measurements were performed on the P3HT films to investigate the influence 
of solvent on the optical properties of the films. The results shows that the UV-vis absorption of P3HT film 
spin-coated from toluene is red shifted compared to the spectra of the films spin-coated from either chloro-
form or 1,2 dichlorobenzene. The surface morphology of P3HT: [6, 6]-Phenyl C61-butyric Acid 3-
ethylthiophene Ester (Modified Fullerene) thin films spin-coated from different solvents were studied us-
ing Atomic Force Microscope (AFM), the thin film spin-coated from 1,2 dichlorobenzene show the smoother 
surface. 
 
Keywords: Poly (3-hexylthiophene), Modified fullerene, Optical properties, Thin films, AFM. 
 
  PACS numbers: 78.66.Qn,78.40.Me  
 
 
                                                          
* bushra_omer4@yahoo.com 
1. INTRODUCTION  
 
Polymer solar cells have shown a potential to har-
ness solar energy in a cost-effective way. The concept of 
generating specific fullerenes that are compatible with 
specific polymers has great potential for increasing the 
performance of bulk heterojunction polymer solar cells 
through the optimization of the morphology. The nano-
morphology of the organic photoactive layer has a 
strong relationship with the performance of the polymer 
solar cells [1]. The morphology of this layer can be 
strongly affected by the processing conditions used such 
as the donor-acceptor composition [2], the solvent and 
the thermal annealing of the organic layer [3, 4]. Sever-
al studies in the literature discussed the effect of solvent 
on the optical and surface morphology of Poly (3-
hexylthiophene-2,5-diyl) (P3HT): [6, 6]-Phenyl C61-
butyric Acid methyl Ester (PCBM) thin films [5, 6]. The 
design and synthesis of modified fullerene with a higher 
LUMO energies compared to PCBM is essential to have 
a higher open circuit voltage and higher efficiency in 
bulk heterojunction polymer solar cells [7, 8, 9]. 
To our knowledge there is no published study on the 
optical and surface morphology of P3HT: [6, 6]-Phenyl 
C61-butyric Acid 3-ethylthiophene Ester (Modified full-
erene) thin films. In this paper we report on the effect 
of preparation conditions on the optical properties of 
the p-type donor polymer P3HT thin films and on the 
surface morphology of the thin films of P3HT: [6, 6]-
Phenyl C61-butyric Acid 3-ethylthiophene Ester. 
 
2. EXPERIMENTS  
 
The p-type donor polymer P3HT and the n-type  
acceptor [6, 6]-Phenyl C61-butyric Acid 3-ethylthiophene 
Ester (modified fullerene) in this study were purchased 
from sigma-Aldrich Corporation and American Dye 
Source, Inc. respectively; the chemical structures are 
shown in Fig. 1. All materials were used as received with-
out further purification. For the UV-vis absorption and 
photoluminescence (PL) measurements, P3HT and P3HT: 
Modified fullerene films were prepared by using spin coat-
ing technique. Chloroform, 1,2 dichlorobenzene and tolu-
ene were used as solvents; the solutions were spin coated 
onto quartz substrates. P3HT films were prepared at the 
concentration of about 11 mg/ml of solvent; the polymer 
solutions were spin-coated at 2000 rpm. The properties of 
the films were obtained on a Lambda-900 UV/Vis/NIR 
spectrophotometer (Perkin Elmer) and on LS55 lumines-
cence spectrometer (Perkin Elmer). 
 
  
 
     a                                        b 
 
Fig. 1 – Chemical structure of (a) poly (3-hexylthiophene-2,5-
diyl) and (b) [6,6]-Phenyl C61-butyric Acid 3-ethylthiophene 
Ester 
 
For surface morphology characterization, P3HT and 
modified fullerene were dissolved in chloroform, 
1,2 dichlorobenzene and toluene to yield a P3HT: modi-
fied fullerene (10.22 : 10.92 mg/ml chloroform, 
10.41 : 10.38 mg/ml 1,2 dichlorobenzene and 
10.50 : 10.56 mg/ml toluene) solutions. The quartz sub-
strates were cleaned by ultrasonic treatment for 
10 minutes using acetone and isopropyl alcohol sequen-
tially. After cleaning of the quartz substrates the solu-
tions were spin coated at 2000 rpm for 40 seconds. The 
surface morphology of P3HT: modified fullerene thin 
films spin coated from different solvents were character-
ized by atomic force microscopy (CP-II veeco). 
 B.M. OMER J. NANO- ELECTRON. PHYS. 5, 03010 (2013) 
 
 
03010-2 
3. RESULTS AND DISCUSSIONS 
 
The UV-vis absorption spectra of P3HT thin films 
spin-coated from chloroform, toluene and 
1,2 dichlorobenzene solutions were recorded. Fig. 2 
shows the UV-vis absorption spectra of the P3HT thin 
films fabricated from the different solvents. For the ab-
sorption spectra of P3HT film fabricated from chloro-
form, wavelength of the absorption peak ( max) is at 
526 nm and two shoulders appeared at 488 nm and 
588 nm. For the P3HT film fabricated from 
1,2 dichlorobenzene, max is 556 nm showing a red-shift 
and clear shoulders appeared at 527 nm and 603 nm. For 
the P3HT film prepared from toluene, the wavelength of 
the absorption peak is the same as the one prepared from 
1,2 dichlorobenzene at 556 nm and the shoulders ap-
peared at 522 nm and 603 nm. The strength of the maxi-
mum peak and the shoulder at higher wavelength of the 
films prepared from 1,2 dichlorobenzene or toluene is in-
creased compared with that prepared from chloroform. It 
was clear that 1,2 dichlorobenzene and toluene promotes a 
higher degree of ordering in P3HT films than chloroform. 
The shift in the peak absorption wavelength in the differ-
ent solvents may be attributed to an increased interchain 
interaction among P3HT chains. The absorption band 
edge of the films using chloroform, 1,2 dichlorobenzene 
and toluene solvents are observed at 660 nm (1.88 eV), 
658 nm (1.89 eV) and 675 nm (1.84 eV), respectively. 
 
 
 
Fig. 2 – The UV-vis spectra of pure P3HT film spin-coated 
from chloroform, 1,2 dichlorobenzene and toluene 
 
The photoluminescence (PL) emission spectra of 
P3HT was recorded in different solvents and are de-
picted in Fig. 3, the photoluminescence spectra do not 
show significant differences. The PL spectrums exhibit 
peaks at 643 nm, 649 nm and 650 nm for the films 
spin-coated from chloroform, 1,2 dichlorobenzene and 
toluene, respectively. The red shift in energy between 
the optical absorption and photoluminescence emission 
peaks is about 117 nm for thin film spin-coated from 
chloroform, 93 nm for the one spin-coated from 
1,2 dichlorobenzene and 94 nm for toluene. Absorption 
and photoluminescence data for P3HT thin films are 
summarized in Table 1. Fig. 4 shows the UV-vis  
absorption spectrum of [6, 6]-Phenyl C61-butyric Acid 
3-ethylthiophene Ester thin film. Two peaks appear at 
266 and 336 nm and there is abroad tail of absorption 
extended to as long as 800 nm. 
 
 
Fig. 3 – The PL spectra of pure P3HT film spin-coated from 
toluene, 1,2 dichlorobenzene and chloroform 
 
 
 
Fig. 4 – The UV-vis absorption of pure Modified Fullerene 
film spin-coated from chloroform 
 
Fig. 5 display the UV-vis spectra of the P3HT: Modi-
fied fullerene (1:1) ratio blended film. The UV-vis ab-
sorption bands of the blend film appeared at 266 nm, 
337 nm, 553 nm and 603 nm. The peaks 266 nm and 
337 nm arise from the modified fullerene; the two other 
peaks with lower energies are caused by P3HT. We 
have extracted the onset wavelength of the blend with 
a linear fit near the absorption edge. The extracted 
onset wavelength was found to be 661 nm (1.88 eV). As 
shown in Fig. 6 the absorption of the films with in-
creasing amount of Modified fullerene reduced signifi-
cantly in the visible range, specifically between 450 nm 
and 650 nm which is the peak absorption wavelength 
band for P3HT. The maximum absorption wavelength 
for all films shows no change. However, in the wave 
length lower than 400 nm, in the range of the peak ab-
sorption of the modified fullerene, the absorption of the 
films with increasing amount of modified fullerene is 
enhanced significantly. It has been reported by Vishal 
Shrotriya et al. [2] that there is a modification in the 
absorption spectra of P3HT:PCBM composite films with 
67 wt % and higher amount of PCBM, the reason is due 
to the presence of PCBM which destructs the ordering 
in the P3HT chains. However, the amount of modified 
fullerene in our study is 50 wt % and less, so it has no 
effect on the chain ordering of P3HT. The film with the 
(3:1) P3HT: Modified fullerene shows the highest ab-
sorption in the range between 450 nm and 650 nm. 
 OPTICAL PROPERTIES OF POLY (3-HEXYLTHIOPHENE-2,5-DIYL)… J. NANO- ELECTRON. PHYS. 5, 03010 (2013) 
 
 
03010-3 
 
 
Fig. 5 – The UV-vis absorption of P3HT: Modified Fullerene 
(1:1) film spin-coated from 1, 2 dichlorobenzene 
 
 
 
 
Fig. 6 – The UV-vis absorption spectra for P3HT: Modified 
fullerene films with different D/A ratio, spin coated from 
1,2 diclorobenzene with spin speed of 2000 rpm.
Table 1 – Optical data of P3HT in thin films spin-coated from different solvents 
 
Solvent  max,UV (nm) onset, (nm) max,PL (nm) Stokes shift (nm) 
Eg  
(eV) 
chloroform 526 660 643 117 1.88 
1,2 dichlorobenzene 556 658 649 93 1.89 
toluene 556 675 650 94 1.84 
 
AFM is a powerful tool to study the nanomorphology 
of organic blends in thin films. The surface topography 
usually gives a good insight into the film formation  
ability and the tendency of the components to phase se-
parate. Fig. 7a displays AFM images of P3HT: Modified 
fullerene blended film prepared from chloroform; the 
area roughness is 8.8 nm. We observe phase separation 
of about 0.2 m. The blended film prepared from 
1,2 dichlorobenzene shows a smooth surface with an 
area roughness of 2.1 nm (see Fig. 7b). We observe a very 
small-scale phase separation (less than 0.1 m) which is 
favorable for charge separation, charge transport, or 
charge collection in polymer solar cells. However, Fig. 7c 
shows that the blended film prepared from toluene have 
a rough surface area with area roughness of 22.5 nm and 
a large-scale phase separation.  
 
     
 
                                  a                                                          b                                                       c            
 
Fig. 7 – AFM images (5  5 m2) of (1:1) P3HT: Modified fullerene film spin coated from (a) chloroform on quartz substrate (area 
roughness  8.83 nm and average height  86.67 nm) (b). 1,2dichlorobenzene on quartz substrate (area roughness  2.11 nm and 
average height  10.42 nm) and (c) toluene on quartz substrate (area roughness  22.49 nm and average height  71.47 nm) 
 
4. CONCLUSIONS 
 
In summary, we have shown that the absorption and 
photoluminescence of P3HT films are dependent on prep-
aration conditions. Further, AFM images were used to 
study the P3HT: Modified fullerene film morphology spin-
coated from different solvents. The results show that the 
surface morphology of the P3HT: Modified fullerene thin 
films depend strongly on the preparation solvent. 
 
AKNOWLEDGEMENTS 
 
Author is grateful to the school of Applied physics 
and the Institute of Microengineering and Nanoelec-
tronics (IMEN), University of Kebangsaan Malaysia for 
unlimited support. 
 
 
 
 
 
 B.M. OMER J. NANO- ELECTRON. PHYS. 5, 03010 (2013) 
 
 
03010-4 
 
REFERENCES 
 
1. A.J. Moule, K. Meerholz, Adv. Mater. 20, 240 (2008). 
2. Vishal Shrotriya, Jianyong Ouyang, Ricky J. Tseng, 
Gang Li, Yang Yang, Chem. Phys. Lett. 411, 138 (2005). 
3. Maher Al-Ibrahim, Oliver Ambacher, Steffi Sensfuss, 
Gerhard Gobsch, Appl. Phys. Lett. 86, 201120 (2005). 
4. Gang Li, Vishal Shrotriya, Yan Yao, Yang Yang, J. Appl. 
Phys. 98, 043704 (2005). 
5. Kenji Kawano, Jun Sakai, Masayuki Yahiro, Chi-
haya Adachi, Sol. Energ. Mater. Sol. C. 93, 514 (2009). 
6. Yladzimir Zhokhavets, Tobias Erb, Gerhard Gobsch, Ma-
her Al-Ibrahim, Oliver Ambacher, Chem. Phys. Lett. 418, 
347 (2006). 
7. C.J. Brabec, A. Cravino, D. Meissner, N.S. Sariciftci, 
M.T. Rispens, L. Sanchez, J.C. Hummelen, T. Fromherz, 
Thin Solid Films 403-404, 368 (2002). 
8. Floris B. Kooistra, Joop Knol, Fredrik Kastenberg, Lacra-
mioara M. Popescu, Wiljan J.H. Verhees, Jan M. Kroon, 
Jan C. Hummelen, Org. Lett. 9, 551 (2007). 
9. Christoph J. Brabec, Antonio Cravino, Dieter Meissner, 
N. Serdar Sariciftci, Thomas Fromherz, Minze T. Rispens, 
Luis Sanchez, Jan C. Hummelen, Adv. Funct. Mater. 11, 
374 (2001). 
 
 


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Optical Properties of Poly (3-hexylthiophene-2,5-diyl) and Poly (3-hexylthiophene-2,5-diyl) / [6,6]-Phenyl C61-butyric Acid 3-ethylthiophene Ester Thin Films

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