Proceedings of the 4th International Conference on Nanostructures (ICNS4) 12-14 March, 2012, Kish Island, I.R Iran Preparation and characterization of doped TiO2 ink to utilize printed electronics F Soheili Najafabadia*, E Adibia, K Aghababaei Samanib, M Hajirasoulihaa a b Research and Development Center, Nano1 Industry, Isfahan 84156-83111, Iran Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran *farsh.s@gmail.com Abstract: In this paper, a technique for fabrication of Ag-doped TiO2 ink by sol-gel process is reported The TiO2 ink is mainly used to prepare of working electrode for dye sensitized solar cells by employing screen printing The prepared ink was characterized by X-ray diffraction, transmission electron microscopy, dynamic light scattering and UV-visible spectroscopy Keywords: Printed electronics; Nano ink; Doped TiO2; Dye sensitized solar cell Introduction There have been growing interests in the development of printed electronics in last few years because printed electronics offer alternatives to traditional silicon techniques and the potential for low cost, large area electronics for flexible displays, sensors and organic solar cells Printed electronics is now increasingly benefiting from recent developments in nanoparticle research and exploiting the advantages of low sintering temperature requirements, which enable the use of low cost substrates Hence, nanoparticles offer new opportunities for manufacturing flexible electronic components and systems The nanometer scale of particles increases the ratio of surface area to volume [1] Because of the advantages of particle size, the sintering temperature of conductive particles such as silver (Ag) and gold (Au) can be reduces below that of their bulk form and their sintering time shortened [1] In addition, nanoparticles have good mechanical properties such as large surface energy and spatial confinement compared to their micron particle size, enabling printing on low cost and temperature sensitive flexible organic substrates [2] Yet nanoparticles have several disadvantages, e.g., long term sedimentation, which sometimes causes them to agglomerate in the printing process even at low temperatures, and maintenance of the stability of the formulated ink at room temperature Some nano inks are preserved by either a dispersant or a polymer shell around the particles and the liquid solvent to improve their stability at room temperature and to guarantee a longer shelf life [3] Accordingly, some general rules can be established for nano inks: (i) nanoparticles should be highly dispersible in their solvent medium, (ii) nanoparticles should be thermally and mechanically stable without aggregation Nanoparticles that use in printed electronics are classified in three main categories: metallic nanoparticles, Ceramic nanoparticles and organic nanoparticles Metallic nanoparticles such as Ag, Au and copper (Cu) are the most investigated metallic elements for formulating ink and understanding their printed film properties [4, 5] In addition, alloying metallic nanoparticles offer better mechanical and electrical properties for printed film like Ag-Cu nano ink [6] Because of their tunable dielectric properties, ceramic nanoparticles are important in high frequency applications In tunable dielectric materials, dielectric properties are tunable under the action of an applied electric or magnetic field Zirconia (ZrO2) and titanium dioxide (TiO2) are examples of ceramic nanoparticles Organic materials are proved to be important phases in the development of printed electronics They have several advantages such as low unit cost, flexibility, robustness and wide applicability In this study, we focus on preparation of metal-doped TiO2 ink that has been used in fabrication of dye sensitized solar cells Recently, dye sensitized solar cells show great promise as inexpensive alternative to conventional silicon solar cell [7] Doping nano-sized TiO2 might enhance photovoltaic efficiency [8] It seems that these phenomena are related to electrical surfacestate modifications induced by metal-ion dopants These modifications lead to significant changes in charge transfer kinetics and dye absorption characteristics In this paper, Ag was chosen as dopant Silver nanoparticles possess the ability to absorb visible light, due to localized surface plasmon resonance (LSPR) [9] In addition, Silver can trap the excited electrons from titanium dioxide and leave the holes for the degradation reaction of organic species It also results in the extension of their wavelength response towards the visible region [10] Experimental All chemicals were purchased from Fluka chemical (Buchs, Switzerland), Aldrich chemical (Milwaukee, WI) and Merck chemical All materials were employed as received In addition, transmission electron microscopy (TEM) image was obtained using a JEOL JEM-2000 Xray diffraction (XRD) pattern of the sample was recorded using a Philips Analytical X pert MPD diffractometer and 333 Proceedings of the 4th International Conference on Nanostructures (ICNS4) 12-14 March, 2012, Kish Island, I.R Iran was analyzed from 10º to 100º (2θ) with a step size of 0.05º and step time of s Dynamic light scattering (DLS) was used to determine size distribution with Malvern ZEN 3600 The UV-visible absorption spectrum was recorded from 200-700 nm by means of Shimadzu, Japan, UV minil 240 spectometer A UH500B Ultrasonic Processor also was used Nanosized Ag-doped TiO2 were prepared by a sol–gel process Titanium tetrachloride (TiCl4) and silver nitrate (AgNO3) were used as precursors of titania and silver, respectively In order to synthesis TiO2 sol, 85 ml of TiCl4 was added to L of distilled water at 0o C, slowly (3ml/20s-3ml/40s) under nitrogen atmosphere at 0o C and stirred for hour This mixture was then subjected under ultrasonic irradiation for 10 to homogenize and was aged at 80 o C for hours The mixture was dried at room temperature until the volume of original solution reached L Then L of tap water was added to the solution (water used should have high quality) and thereafter, to concentrate the solution to ½ of its initial volume, a ceramic membrane was used After addition of L of tap water, the membrane was washed for subsequent applications When the volume of original solution reached L, to adjust pH of the solution to 1.8, L additional tap water was added to it The resultant product will be TiO2 sol In next step, Ag-doped TiO2 ink was prepared by photoreducting Ag+ ions to Ag metal on the TiO2 3.2 g of AgNO3 and 100 ml of TiO2 sol were added to mixture of distilled water and Ethylene glycol under controlled temperature The resultant solution was stirred to homogenize and then was treated by ultrasonic irradiation The mixture was then irradiated with UV light by eight mercury lamps (8w) for hours The nanostructure of the sample was measured by TEM The TEM image of Ag-doped TiO2 nanoparticles in the Fig shows that the dimension of the nanoparticles is 20-25 nm Fig TEM image of Ag-doped TiO2 (bar=30 nm) Fig represents size distribution of the sample measured by DLS From the DLS profile, we observe that the size of nanoparticles is mostly between 18 to 32 nm 27.7% and 27.2% of nanopartcles are 24 nm and 21 nm, respectively Fig Size distribution of the Ag-doped TiO2 Results and Discussion Fig illustrates the XRD profile of Ag-doped TiO2 The XRD pattern of the sample revealed anatase as the predominant homogeneous crystalline phase Fig UV-vis absorption of Ag-doped TiO2 sol UV-visible absorption profile of the Ag-doped TiO2 sol is illustrated in Fig The marked wavelength shows absorption peak that occurs in 410 nm Conclusions Fig XRD pattern of Ag-doped TiO2 sol 334 Printed electronics with various functional inks have been expected to grow rapidly as a mass production Proceedings of the 4th International Conference on Nanostructures (ICNS4) 12-14 March, 2012, Kish Island, I.R Iran process for new types of electronic equipments Thus, the present study outlines the procedure and characterization of Ag-doped TiO2 ink that mostly used in preparation of dye sensitized solar cells by using printed electronics The size of nanoparticles was mainly 24 nm measured by DLS The major phase of the synthesized particles was anatase that analyzed by XRD References [1] P Buffat, J P Borel, “Size effect on the melting of gold particles”, Physical Review A, 13 (1976) 2287 [2] S H Ko, et al., “Air stable high resolution organic transistors by selective laser sintering of inkjet printed metal nanoparticles”, Applied Physics Letter, 90 (2007) 141103 [3] U Caglar, K Kaija, P Mansikkamaki, “Analysis of mechanical performance of silver printed structures”, Proc of the 2nd IEEE International Nanoelectronics Conference, Shanghai, China, 2008, 851-856 [4] N R Bieri, J Chung, S E Haferl, D Poulikakos, “Microstructuring by printing and laser curing of nanoparticle solutions”, Applied Physics Letter, 82 (2003) 3529 [5] D Huang, F Liao, S Molesa, D Redinger, V Suramanian, “Plastic-compatible low resistance printable gold nanoparticle conductors for flexible electronics”, Journal of the Electrochemical Society, 150 (2003) G412 [6] S Gamerith, A Klug, H Scheiber, U Scherf, E Moderegger, E J W List, “Direct inkjet printing of AgCu nanoparticle and Ag-precursor based electrodes for OFET applications”, Journal of Advanced Functional Materials, 17 (2007) 3111 [7] M Grätzel, “Dye-sensitized solar cells”, Journal of Photochemistry and Photobiology C: Photochemistry Reviews, (2003) 145 [8] K H Ko, Y C Lee, Y J Jung, “Enhanced efficiency of dye-sensitized TiO2 solar cells (DSSC) by doping of metal ions”, Journal of Colloid and Interface Science, 283 (2005) 482 [9] N Halas, “Playing with plasmons Tuning the optical resonant properties of metallic nanoshell”, MRS Bulletin, 30 (2005) 362 [10] V Iliev, D Tomova, L Bilyarska, A Eliyas, L Petrov, “Photocatalytic properties of TiO2 modified with platinum and silver nanoparticles in the degradation of oxalic acid in aqueous solution ”, Applied Cataysis B, 63 (2006) 266 335 ... Ag -doped TiO2 ink was prepared by photoreducting Ag+ ions to Ag metal on the TiO2 3.2 g of AgNO3 and 100 ml of TiO2 sol were added to mixture of distilled water and Ethylene glycol under controlled... Kish Island, I.R Iran process for new types of electronic equipments Thus, the present study outlines the procedure and characterization of Ag -doped TiO2 ink that mostly used in preparation of dye... DLS profile, we observe that the size of nanoparticles is mostly between 18 to 32 nm 27.7% and 27.2% of nanopartcles are 24 nm and 21 nm, respectively Fig Size distribution of the Ag -doped TiO2