Surface Photo-Voltage (SPV) and Photo electrochemistry (PEC) on TiO2

Abstract

Surface charge transfer processes at semiconductors have been of great importance as the quality of the material is vital in various applications such as electronics, photovoltaics, catalysis, electrocatalysis, photocatalysis, battery, supercapacitors to name but a few. Surface Photo-voltage (SPV) is a unique and simple technique based on the spectral dependence of the photovoltage as a function of photon energy applied as non-destructive and contactless method. It has been applied for the characterization of semiconductors such as band gap, surface potential, doping concentration, especially the minority carrier lifetime and diffusion length correlating to size, shape, thickness etc. Its simplicity including sample preparation, contacts, junction formation, etc. is an advantage over several other spectroscopic methods since it can offer information on submerged heterostructure layers.We will present characterization of several size and shapes of TiO2 (thin films, nanorods, etc.) towards its hole diffusion length using SPV (solid/solid) and compared with photoelectrochemical (PEC) technique (solid/liquid). We will point out the application of SPV and PEC on TiO2 coated LiCoO2, for possible insight on the stability and increased capacity in LIB (lithium-ion battery) from a thermodynamic and kinetic point of view. We will discuss the application of SPV technique in understanding the mechanism related to decreased surface oxygen activity and change in the activation energy of Li ion transfer.