preparation and characterization of doped tio2 ink to ultilize printed electronics

Preparation and characterization of doped TiO2 ink to utilize printed electronics F.. The TiO2 ink is mainly used to prepare of working electrode for dye sensitized solar cells by employ

Preparation and characterization of doped TiO2 ink to utilize printed electronics

F Soheili Najafabadia*, E Adibia, K Aghababaei Samanib, M Hajirasoulihaa a

Research and Development Center, Nano1 Industry, Isfahan 84156-83111, Iran

b 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 mightenhance photovoltaic efficiency [8] It seems that these phenomena are related to electrical surface-state 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 X-ray diffraction (XRD) pattern of the sample was recorded using a Philips Analytical X pert MPD diffractometer and

was analyzed from 10º to 100º (2θ) with a step size of

0.05º and step time of 1 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 2 L of distilled water at 0o C, slowly

(3ml/20s-3ml/40s) under nitrogen atmosphere at 0o C and

stirred for 1 hour This mixture was then subjected under

ultrasonic irradiation for 10 min to homogenize and was

aged at 80 o C for 2 hours The mixture was dried at room

temperature until the volume of original solution reached

1 L Then 1 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 1 L of tap

water, the membrane was washed for subsequent

applications When the volume of original solution

reached 1 L, to adjust pH of the solution to 1.8, 1 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 4 hours

Results and Discussion

Fig 1 illustrates the XRD profile of Ag-doped TiO2 The

XRD pattern of the sample revealed anatase as the

predominant homogeneous crystalline phase

Fig 1 XRD pattern of Ag-doped TiO2 sol

The nanostructure of the sample was measured by TEM The TEM image of Ag-doped TiO2 nanoparticles in the Fig 2 shows that the dimension of the nanoparticles is 20-25 nm

Fig 2 TEM image of Ag-doped TiO2 (bar=30 nm) Fig 3 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 3 Size distribution of the Ag-doped TiO2

Fig 4 UV-vis absorption of Ag-doped TiO2 sol

UV-visible absorption profile of the Ag-doped TiO2 sol is illustrated in Fig 4 The marked wavelength shows absorption peak that occurs in 410 nm

Conclusions

Printed electronics with various functional inks have been expected to grow rapidly as a mass production

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

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