Study Of Photonic Crystals Structure & Spr Of AU Nanoparticles Used For Dye-sensitized Solar Cell

Low cost, light in weight, workable in weak light - TFSC (thin film solar cell) emerged in recent years as a promising material of 3rd generation solar energy application. Beside TFSCs based on CIGS (CuInGaSe), CdTe and Amorphous Si:H, which have been commercialized and produced in mass, dye sensitized solar cell (DSSC) developed by Gr?tzel team also attracted much attention, because of its cheap but abundant raw materials and its simple manufacture procedures. DSSC replaced conventional flat electrode by a mesoporous nanocrystalline TiO₂ film sensitized by a ruthenium dye as the e-donor, and thus push the efficiency up to 11%. TiO₂ as the cathode material of the solar cell is not only important in absorbing sun light, but also functioning as the carrier of dye molecules and the receptor of e- before transferring e- to electrode. Therefore, the physical properties and the microstructure of TiO₂ are crucial to the cell's efficiency.On the other hand, the concept of"photonic crystal", introduced by S. John and E. Yablonoviteh, represents dielectric materials structured periodically, in order to control the properties of light passing through. Recently, structure engineering also drew tremendous attention for its applications in photoelectochemical solar cells; according to some reports, highly-ordered macroporous structured materials can contribute to light absorption.Our project was dedicated to the study of employing photonic crystal structure to improve light harvesting efficiency in solar cell. To be more specific, to prepare a highly-ordered macroporous TiO₂ thin film as the electrode, and thus circumvent the low light absorbing limit as a bottle-neck of Dye-Sensitized Solar Cell. Moreover, we have tried to dope the electrode surface with Au nano-particles to further increase the light absorption abilities. Theoretically, as the Au NPs has prominent surface plasmon resonance (SPR) effect, the SPR waves around Au NPs modulated by the periodic architectures of Photonic Crystals can induce a local coherent oscillation mode, and thus amplify the light harvesting efficiency and promote the photo-electronconversion in the solar cell. We firstly realized this structure trough a templating method and later tested its photonic and electric properties.To prepare the opaline-structured template, we use?a nonsoap emulsion polymerization?method; and realized a 2⁴μm thick of Polystyrene(PS) film by a vertical deposition method, composed by PS colloid spheres of 200²30nm in size.Based on these opal-templates, some highly-ordered macroporous anatase titania films were synthesized through topology. In the process, we first filled the template with a TiO₂ precusor formerly prepared by sol-gel method and then sintered at 450℃in furnace, which resulted in a highly-ordered inverse-opal structure with pore diameter at 150nm²20nm. In order to improve the macroporous surface quality, we initiated a new"Sandwich"filling method, and analysed different parameters in gel-filling, aging and sintering stages, based on SEM photos, XRD pattern and TGA curve.After successfully synthesized 10¹00nm Au NPs by the?Reduction?of?Citrate, we tried to coat the TiO₂ films with 10²0nm Au NPs using a simple solvent-vaporing method. TEM characterized Au's shapes and SEM photos shown the 10²0nm Au NPs uniformly dispersed into the holes; the spectrophotometer tested those films'light absorption spectrums before and after doping the Au NPs, the result proved that doping Au can enlarge the absorption spectrum, thus has potential usefulness in cell's light absorption.Sensitized with N3-dye, we used these Au-doped inverse-opals TiO₂ films as the electrode in a Dye-synthesized Solar Cell (DSSC); went through I-V response tests and calculated calls'key parameters. Experiment results have proven that photonic crystal structure can raise the Isc (Short circuit current) by nearly 150%, and Au doping can improve the FF (filing factor), the cell's efficiency was doubled by the combining effect. These cells may be promising for future applications in solar cell to increase light harvesting effect and improve the cell's efficiency.