STRUCTURE AND PROPERTIES OF VISIBLE-LIGHT ABSORBING HOMODISPERSE NANOPARTICLES

Structure and Properties of Visible Light Absorbing Homodisperse Nanoparticles The project’s goal is to relate the physical properties of homodisperse polyoxotitanate and quantum-dot cadmium chalcogenide (CdS and CDSe) nanoparticles to their detailed experimental structure as determined by X-ray diffraction of the crystalline materials. Using both solution and solvothermal methods we synthesize and subsequently crystallize a large number of homodisperse Ti- and Cd-based, ‘pure’, doped, and functionalized nanoparticles of up to 3 nm dimensions. Photo-excited electron-donating Cd-based nanoparticles are to be connected throughconducting linkerstoelectron-accepting Ti-particlesto yield models for quantum-dot sensitized solar cells. Structure and properties are obtained by crystallographic and very fast transient spectroscopic measurements, as well as by theoretical and electrochemical methods. The resulting information is subsequently interpreted by theoretical calculation of the electronic structure and the electron injection dynamics. The spectral range of the absorption of light and the resulting charge injection are of prime importance for the photovoltaic properties of the materials and the operation of photovoltaic cells. How do the properties depend on the detailed structure and on the nature of doped atoms and attached chromophores? How do the dynamics of charge injection and subsequent charge recombination affect the efficiency of the light harvesting? To obtain insight in the latter we combine the structural and chemical information with ultrafast transient spectroscopy measurements. Photo-electrochemical measurements on thin films of the nanoparticles deposited on an electrode are performed to check the electron or hole injection nature of the charge transfer and get additional information on the wavelength-dependence of the charge injection. The project has several components: Synthesis and crystal growth of new phases with series of dopants, static and transient spectroscopy, crystallography, theoretical calculations, electrochemical characterization of the new sensitizing solids.