Sains Malaysiana 42(8)(2013): 1151–1157

Optical Properties of Poly( 9,9’-di-n-octylfluorenyl-2.7-diyl)/Amorphous SiO₂

Nanocomposite Thin Films

(Sifat Optik Filem Nipis Nanokomposit Poli( 9,9’-di-n-ostilfluorenyl-2.7-diil)/Amorfus SiO₂)

Mohammad Hafizuddin Haji Jumali¹*, Bandar Ali Al-Asbahi^1,2& Chi Chin Yap¹, Muhamad Mat Salleh³& Mohamad Saleh AlSalhi⁴

¹School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, D.E. Malaysia

²Department of Physics, Faculty of Science, Sana’a University, Yemen

³Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, D.E. Malaysia

⁴Department of Physics and Astronomy, Laser Group, College of Science

King Saud University, Saudi Arabia

Received: 11 June 2012 / Accepted: 2 February 2013

ABSTRACT

Identified as potential materials for optoelectronic applications, the polymer/inorganic nanocomposites are actively studied. In this work, the effect of amorphous silica nanoparticles (NPs) content on the optical properties of Poly (9,9’-di-n-octylfluorenyl- 2.7-diyl) (PFO) thin films has been investigated. Different ratios of PFO/SiO₂ NPs composites have been prepared using solution blending method. Then, the blends were spin-coated onto glass substrates at 2000 rpm for 30 s and subsequently dried at room temperature. XRD and TEM were used to determine the structural properties, while UV-Vis and PL spectrophotometers were employed to investigate the optical properties of the films. XRD confirms that there was no variation on structure of both PFO and SiO₂ NPs resulted from the blending process. TEM micrographs display that majority of amorphous SiO₂ NPs were well coated with PFO. The absorption spectra of the composite thin films were red-shifted, indicating the increment in conjugation length of the PFO/SiO₂ composite. In addition, the calculated values of the optical energy gap, the width of the energy tails and vibronic spacing of the composite films exhibited SiO₂ content dependence.

Keywords: Absorption; energy gap; energy tail; photoluminescence; vibronic spacing

ABSTRAK

Dikenal pasti sebagai bahan berpotensi untuk kegunaan optoelektronik, nanokomposit polimer/bahan inorganik sedang dikaji secara aktif. Dalam kajian ini kesan kandungan nanozarah amorfus SiO₂ ke atas sifat optik filem nipis poli(9,9’-di-n-ostilfluorenyl-2.7-diil) (PFO) telah dikaji. Larutan PFO/SiO₂ yang berbeza nisbah telah disediakan menggunakan teknik adunan larutan. Kemudian, adunan dimendapkan ke atas substrat kaca menggunakan teknik salutan berputar pada kelajuan 2000 ppm selama 30 s dan seterusnya dikeringkan pada suhu bilik selama 1 jam. XRD dan TEM digunakan untuk pencirian struktur sementara spektrofotometer UV-Vis dan PL digunakan untuk mengkaji sifat optik filem yang disediakan. Pencirian XRD tidak menunjukkan sebarang perubahan struktur ke atas PFO dan nanozarah SiO₂ akibat dari proses adunan. Mikrograf TEM menunjukkan nanozarah amorfus SiO₂ tersalut oleh PFO. Berbanding spektrum penyerapan filem PFO, spektrum penyerapan untuk filem nipis nanokomposit mempamerkan anjakan merah, menandakan pertambahan panjang konjugasi PFO/SiO₂. Selain itu, nilai bagi jurang tenaga, lebar ekor tenaga dan jarak vibronik oleh filem komposit juga menunjukkan pergantungan kepada kandungan SiO₂.

Kata kunci: Ekor tenaga; fotoluminesen; jarak vibronik; jurang tenaga; penyerapan

REFERENCES

Al-Ani, S.K.J., Al-Ramadin, Y., Ahmad, M.S., Zihlif, A.M., Volpe, M., Malineonico, M., Martuscelli, E. & Ragosta, G. 1999. The optical properties of polymethylmethacrylate polymer dispersed liquid crystals. Polymer Testing 18(8): 611-619.

Assaka, A.M., Rodrigues, P.C., De Oliveira, A.R.M., Ding, L., Hu, B., Karasz, F.E. & Akcelrud, L. 2004. Novel fluorine containing polyfluorenes with efficient blue electroluminescence. Polymer 45(21): 7071-7081.

Bajpai, M., Srivastava, R., Kamalasanan, M.N., Tiwari, R.S. & Chand, S. 2010. Charge transport and microstructure in PFO: MEH-PPV polymer blend thin films. Synthetic Metals 160(15-16): 1740-1744.

Carter, S.A., Scott, J.C. & Brock, P.J. 1997. Enhanced luminance in polymer composite light emitting devices. Applied Physics Letters 71:1145.

Dow, J.D. & Redfield, D. 1970. Electroabsorption in semiconductors: The excitonic absorption edge. Physical Review B 1(8): 3358-3371.

Dutta, K. & De, S.K. 2006. Transport and optical properties of SiO2–polypyrrole nanocomposites. Solid State Communications 140(3-4): 167-171.

Elliott, S.R. 1998. The Physics and Chemistry of Solids. London: J. Wiley.

Ginger, D.S. & Greenham, N.C. 1999. Charge separation in conjugated-polymer/nanocrystal blends. Synthetic Metals 101(1-3): 425-428.

Hagler, T.W., Pakbaz, K., Voss, K.F. & Heeger, A.J. 1991. Enhanced order and electronic delocalization in conjugated polymers oriented by gel processing in polyethylene. Physical Review B 44(16): 8652-8666.

Han, Z., Zhang, J., Yang, X., Zhu, H. & Cao, W. 2010. Synthesis and application in solar cell of poly(3-Octylthiophene)/titania nanotubes composite. Organic Electronics 11(8): 1449-1460.

Ho, P.K.H. & Friend, R.H. 2002. Π-electronic and electrical transport properties of conjugated polymer nanocomposites: Poly (P-Phenylenevinylene) with homogeneously dispersed silica nanoparticles. The Journal of Chemical Physics 116: 6782-6795.

Huang, Y., Qin, Y., Zhou, Y., Niu, H., Yu, Z-Z. & Dong, J-Y. 2010. Polypropylene/graphene oxide nanocomposites prepared by in situ Ziegler−Natta polymerization. Chemistry of Materials 22(13): 4096-4102.

Ibrahim, S., Ahmad, R. & Johan, M.R. 2012. Conductivity and optical studies of plasticized solid polymer electrolytes doped with carbon nanotube. Journal of Luminescence 132(1): 147-152.

Jafarzadeh, M., Rahman, I.A. & Sipaut, C.S. 2009. Synthesis of silica nanoparticles by modified sol–gel process: The effect of mixing modes of the reactants and drying techniques. Journal of Sol-gel Science and Technology 50(3): 328-336.

Kickelbick, G. 2003. Concepts for the incorporation of inorganic building blocks into organic polymers on a nanoscale. Progress in Polymer Science 28(1): 83-114.

Kim, K-S. & Park, S-J. 2012. Influence of N-doped Tio₂ on lithium ion conductivity of porous polymeric electrolyte membrane containing LiClO4. Solid State Ionics 212: 18-25.

Liu, D., Teng, F., Xu, Z., Yang, S., Qian, L., He, Q., Wang, Y. & Xu, X. 2007. Enhanced brightness and efficiency in organic light-emitting diodes using SiO₂ as buffer layer and electron-blocking layer. Journal of Luminescence 122-123: 656-659.

Liu, J., Shi, Y. & Yang, Y. 2001. Improving the performance of polymer light-emitting diodes using polymer solid solutions. Applied Physics Letters 79: 578-580.

Peng, F., Lu, L., Sun, H., Wang, Y., Liu, J. & Jiang, Z. 2005. Hybrid organic-inorganic membrane: Solving the tradeoff between permeability and selectivity. Chemistry of Materials 17(26): 6790-6796.

Pichler, K., Halliday, D.A., Bradley, D.D.C., Burn, P.L., Friend, R.H. & Holmes, A.B. 1993. Optical spectroscopy of highly ordered poly (P-Phenylene Vinylene). Journal of Physics: Condensed Matter 5: 7155-7172.

Raja, V., Sarma, A.K. & Rao, V.V.R. 2003. Optical properties of pure and doped Pmma-CO-P4VPNO polymer films. Materials Letters 57(30): 4678-4683.

Rozenberg, B.A. & Tenne, R. 2008. Polymer-assisted fabrication of nanoparticles and nanocomposites. Progress in Polymer Science 33(1): 40-112.

Tommalieh, M.J. & Zihlif, A.M. 2010. Optical properties of polyimide/silica nanocomposite. Physica B: Condensed Matter 405(23): 4750-4754.

Uragami, T., Matsugi, H. & Miyata, T. 2005. Pervaporation characteristics of organic-inorganic hybrid membranes composed of poly (vinyl alcohol-co-acrylic acid) and tetraethoxysilane for water/ethanol separation. Macromolecules 38(20): 8440-8446.

Urbach, F. 1953. The long-wavelength edge of photographic sensitivity and of the electronic absorption of solids. Physical Review 92: 1324.

Yang, S.H., Le Rendu, P., Nguyen, T.P. & Hsu, C.S. 2007. Fabrication of MEH-PPV/SiO2. Reviews on Advanced Materials Science 15: 144-149.

Yang, S.H., Nguyen, T.P., Le Rendu, P. & Hsu, C.S. 2005. Optical and electrical investigations of poly (P-Phenylene Vinylene)/ silicon oxide and poly (P-Phenylene Vinylene)/titanium oxide nanocomposites. Thin Solid Films 471(1-2): 230-235.

*Corresponding author; email: hafizhj@ukm.my