*3.3.1 TiO2 Nanoparticles prepared by 2-step hydrothermal treatment*

Anatase TiO2 NPs were investigated by using a field-emission scanning electron microscope (SEM, S4800, Hitachi) and JEOL-2010 TEM (JEOL, Japan) equipped with an energy dispersive spectrometer (EDS) to investigate the TiO2 NPs and determine

*A New Generation of Energy Harvesting Devices DOI: http://dx.doi.org/10.5772/intechopen.94291*

#### **Figure 5.**

tertrabutylammonium hydroxide and then purified three times with chromatography. (Sephadex LH-20) The pH values below 4.5 is controlled by 0.02 M HNO3. The titration is carried out slowly over a period of three hours. Then, the solution is kept at -20°C for 15 hours. After allowing the flask to warm to 25°C, the precipitated

he liquid electrolyte was prepared by dissolving 0.6 M of 1- butyl-3-methylimi-

Even if tBP and Li<sup>+</sup> ions play a different role for solar cell performance, both additives are widely used in liquid electrolyte. As another effective additive, adding GuSCN can be also good choice. It shifts the conduction band edge of TiO2 toward

The cathode-electrode was produced by coating F:SnO2 glass with a thin layer of a 5 mM solution of H2PtCl6 in isopropanol and was heated at 400°C for 20 min. Best performance and long-tern stability has been achieved with very low Pt-loadings

A paste of anatase hydrothermal TiO2 powder was made by stirring with the mixture 0.5 g of anatase-TiO2 NPs, 100 μl of Triton X-100, 0.2 g of polyethylene glycol (PEG, Fluka, Mw = 20,000) into 3 ml acetic acid (0.1 M). The TiO2 paste is coated on a FTO glass by doctor blade technique. The thickness of the TiO2 film was measured by a surface profiler (TENCOR. P-10) [26, 51]. **Figure 4(d)** and **(e)** gives an illustrative sequence of steps that were used in the fabrication of our solar cells. The top and bottom electrodes were sandwiched together with thermal melt polymer film (**Figure 4e**).

Anatase TiO2 NPs were investigated by using a field-emission scanning electron microscope (SEM, S4800, Hitachi) and JEOL-2010 TEM (JEOL, Japan) equipped with an energy dispersive spectrometer (EDS) to investigate the TiO2 NPs and determine

), so that the counter electrode remains transparent. Charge transfer

lower energies, suggesting adsorption of the cation onto the TiO2 surface. Coadsorbants, adsorbed onto the TiO2 during the dye adsorption procedure, can

dazolium iodide (**BMII**), 0.03 M of iodine, 0.1 M of guanidinium thiocyanate (**GuSCN**) and 0.5 M of 4-tert-butylpyridine (**tBP**) in acetonitrile and valeronitrile (85:15 v/v). Most additives are understood at a fairly phenomenological level, and their effects are often attributed to modification of redox couple potential, band shifts of the semiconducting electrode material, effects of surface blocking, or surface dye organization. The study for additives have been reviewed extensively elsewhere [47, 48]. For example, it was found that smaller size Li<sup>+</sup> ions cause a shift in the TiO2 conduction band edges toward more positive potentials than larger size 1,2-dimethyl-3-hexylimidazolium ions. As a result, an electrolyte containing Li<sup>+</sup> ions produced a lower photovoltage and at the same time higher photocurrent than that containing imidazolium cations because of an alteration of both the energy and number of excited state levels of the dye that participate in electron injection [46]. The effects of tBP were studied in more detail in DSSCs showing that both band

complex is collected on a glass frit and air dried.

*Solar Cells - Theory, Materials and Recent Advances*

edge shift and increased electron lifetime play a role [49].

have similar effects as additives in the electrolytes [50].

resistances of less than 1 Ω cm<sup>2</sup> can be achieved.

**3.3 DSSC fabrication for conventional typed cell**

*3.3.1 TiO2 Nanoparticles prepared by 2-step hydrothermal treatment*

*3.2.3 Liquid electrolyte*

*3.2.4 Catalytic layer*

(5 μg cm<sup>2</sup>

**196**

*(a) X-ray diffraction patterns of hydrothermal TiO2 nanoparticle after calcination at 500oC. Insert shows the SEM images of nanopaticle after calcination. (b) a.TEM, b. SEAD pattern, c. HR-TEM bright field images and d. EDX analysis of TiO2 nanocrystals prepared by 2-step autoclaving technique scheme showing a typical procedure for highly crystalline TiO2 nanoparticle based DSSC.*

the compositions of the samples at 200 kV. The NPs were also characterized by x-ray diffraction (D/Max-A, Rigaku) measurements. **Figure 5(a)** shows a X-ray scan of the Anatase TiO2 NPs before and after sintering as described below. The inset shows a typical SEM photo of the NPs used in the experiment. These results reveal broad diffraction peaks at 25.3°, 37.8°, 48.2°, 53.9° and 55.2° were observed, which can be indexed to the (101), (004), (200), (105) and (211) reflections of anatase TiO2. **Figure 5(b)** provides the high resolution transmission microscopic (TEM) images and selected area electron diffraction pattern of the TiO2 NPs. It provides the corresponding electron diffraction pattern taken from the TiO2 NPs showing that the NPs are crystalline Anatase TiO2. **Figure 5(b)** gives the high-resolution TEM (HRTEM) image of NPs indicating that the TiO2 NPs are single-crystalline. Lattice of 0.189 nm and 0.243 nm corresponding to (200) and (103) planes of the tetragonal TiO2, respectively, have been resolved. The inset is the corresponding fast Fourier transform (IFFT) image of selected area in **Figure 5(b)c**. In **Figure 5(b)d** the EDS taken from TiO2 NPs shows that the NPs are composed of Ti and O. The Cu peak comes from the grid. From these measurements, we concluded that our starting materials were pure Anatase.
