xxiii πανελληνιο ÏƒÏ Î½ÎµÎ´ÏÎ¹Î¿ Ï†Ï ÏƒÎ¹ÎºÎ·Ï‚ στερεας καταστασης & επιστημης ...

Templated Sol-Gel Synthesis Of TiO 2 Nanoparticles
Presenting Nanowire-Like Structure For Dye-Sensitized
Solar Cells
N. Alexaki, T. Stergiopoulos, A. G. Kontos, D. Tsoukleris, P. Falaras
Institute of Physical Chemistry, NCSR Demokritos, 15310 Aghia Paraskevi Attikis, Athens, Greece
*papi@chem.demokritos.gr
Several works have been directed toward optimizing the efficiency of dye-sensitized solar cells (DSSCs) by developing
novel methods of nanotitania synthesis and deposition on TCO. Functional properties of TiO 2 are influenced by many
factors such as crystallinity, particle size and surface area and all these parameters are related to different conditions of
preparation. Very recently, this work has been focused on preparing nanoparticles in the form of wires and tubes [1].
Sol-gel process is favoured as an appropriate way for preparing nanomaterials because by the correct
template choice, alkoxide precursor concentration, hydrolysis-condensation reaction conditions and sintering
temperature important parameters such as particle size, film thickness and porosity can be readily controlled [2].
Nanocrystalline titania was synthesized by a sol-gel method using tetraisopropyl orthotitanate (TIPT) modified with
acetylacetone (ACA)/alkylamine hydrochloride [3]. In this work, results with hexadecylamine-based synthesis are
reported.
The progress of reaction was observed by XRD and Raman (Figure 1). The reaction seems to end in the first
two days (by forming crystalline titania) and only a slight increase in the particles size from about 4.78 nm to 5.39 nm
was observed.
Figure1: Raman and XRD results of titania powder during the days of reaction
The next step was the preparation of titania films and their incorporation as photoelectrodes into a solar cell
configuration. The films were deposited on TCO by preparing a paste made of pure nanocrystalline titania and water
(ratio 1:2 w/w). Several films were prepared and calcined at different temperatures (400 o C, 450 o C, 500 o C, 550 o C). The
characterization of these titania films was made by XRD and Raman. No particular differences were observed
regarding the films’ morphology and crystallinity. This is why only figures concerning 550 0 C are depicted.
Nevertheless, slight differences were observed related to the particle size and crystalline polymorphism (Table 1).
Temperature ( o C ) Particle size (nm) Rutile ratio (%) Anatase ratio (%)
without calcination 5.39 - 100.00
400 6.47 7.15 92.85
450 7.17 10.34 89.66
500 7.90 14.48 85.52
550 11.88 14.74 85.26
Table 1: Differences of particles size and rutile to anatase ratios with the increase of temperature (taken from XRD
data)
210