**5. Nanostructures TiO2 electrode in DSSC from 0 to 3 dimensions**

As the main core of DSSCs, the nanocrystalline morphology of the photoelectrode film is critical for the efficient operation. Large efforts have been paid to optimize the morphology of the nanostructured photoanodes with improved architectures for high dye loading and fast electron transport. Although 2-step HT-NPs films treated with the interfacial modification have been regarded as a paradigm of porous photoelectrode for use in DSSCs, there are still challenges to boost the photovoltaic performance or competitiveness. Therefore, the metal oxides in their nanoform can be synthesized under various morphologies with different shapes and sizes, thus offering the possibility for modulating their properties. In literature, a variety of preparation techniques, such as sol–gel, [87] hydrothermal/ solvothermal, [88] electrochemical anodization, [89] electrospinning, [35] spray pyrolysis, [90] and atomic layer deposition [91], have been developed and applied

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

represent the best fits from our modeling calculations. The fitting parameters are tabulated in **Table 3**. (the photoanode comprised 11 μm thick TiO2 film and approximately 0.332 cm2 active area with mask). The DSSC with the Ag film and 3D PCs showed higher short-circuit current densities and solar-to-electric conversion efficiencies than the traditional DSSC. For the Ag film, the short-circuit current

and fill factor were almost identical; and the solar-to-electric conversion efficiency

cies were enhanced by 1.94, 7.78, 10.7, 11.3 and 14.4% for the 198 nm, 311 nm, 375 nm, 410 nm, and double layer (375/410 nm), respectively, as compared to the traditional typed DSSC. The 3D PC with 198 nm sized PhC showed the lowest efficiency enhancements because the traditional DSSC absorbed most of the light, this corresponds to the reflection peak of this PhC, as shown in **Figures 13(c)** and **14(c)**. The 375 nm and 410 nm sized PhC showed high enhancements in the solarto-electric conversion efficiencies because the traditional DSSC transmitted more than 50% of the light; this corresponds to the reflection peaks of these PhC. This enhancement in the solar-to-electric conversion efficiencies is higher than that in the Ag film even though the Ag film has a considerably higher reflection intensity; this can be explained by the diffraction effect of the PhC as shown in **Figure 14(b)**. The PhC with 375/410 nm double layers showed highest enhancements in the solarto-electric conversion efficiencies because the double layer PhC has a significant overlap with the quantum efficiency spectra of the ruthenium dye; moreover, the diffraction effect of the PhC is also present. From **Table 3**, the multilayer whose PBG has a large overlap with the quantum efficiency spectra of the ruthenium dye leads to larger enhancements in the photocurrent. Furthermore, the PhC -based DSSC exhibits considerably higher short circuit photocurrents than the traditional

In the case of the DSSCs with 3D PhCs, the solar-to-electric conversion efficien-

The generation of photocurrent is primarily influenced by the light absorption of the dye. Therefore, when coupling PhC with the back surface of the DSSC, light absorption is increased attributed to the reflection and diffraction of light. This directly reflect the enhancement of the short-circuit current densities and the overall efficiency, while the open-circuit voltage, fill factor is unaffected. The DSSC with the PhC of 375, 410 nm and double layer diameters showed higher conversion efficiency than that with the Ag film; this can be explained not only by the reflection but also the diffraction effect in the DSSCs. As a result, we demonstrated here that recycling of photons by PhC is an effective way to increase the cell efficiency.

**5. Nanostructures TiO2 electrode in DSSC from 0 to 3 dimensions**

photoelectrode film is critical for the efficient operation. Large efforts have been paid to optimize the morphology of the nanostructured photoanodes with improved architectures for high dye loading and fast electron transport. Although 2-step HT-NPs films treated with the interfacial modification have been regarded as a paradigm of porous photoelectrode for use in DSSCs, there are still challenges to boost the photovoltaic performance or competitiveness. Therefore, the metal oxides in their nanoform can be synthesized under various morphologies with different shapes and sizes, thus offering the possibility for modulating their properties. In literature, a variety of preparation techniques, such as sol–gel, [87] hydrothermal/ solvothermal, [88] electrochemical anodization, [89] electrospinning, [35] spray pyrolysis, [90] and atomic layer deposition [91], have been developed and applied

As the main core of DSSCs, the nanocrystalline morphology of the

; the open-circuit voltage

densities were increased by approximately 0.84 mA/cm<sup>2</sup>

*Solar Cells - Theory, Materials and Recent Advances*

DSSC and is much more effective than the conventional Ag film.

was enhanced by 5% .

**210**

**Figure 16.** *SEM images of different types of 0D 1D 2D 3D- TiO2. Produced in our lab.*

to obtain different morphologies in photoanode materials. In this study, a variety of nanostructures from zero dimensional (0D) to three dimensional (3D) has been tested. Electro-spinning and spraying technique has been adopted to prepare the the different dimensional metal oxide semiconductor film by controlling the polymer host and solvents. The detailed results can be seen in followed section (**Figure 16**).
