Fabrication and Characterization of Germanium Doped Titanium Dioxide (Ge:TiO2)Thin Film for Photovoltaic Application

Abstract

This study intends to realize 3 novel thin film material for photovo ltaic appl ications. Ti02 that has a I3rge band gap of 3.2eV is sensitized to visible light via the use of dyes in the Gratzel cell. The dye monolayer when excited by light photons. electron-hole pairs are generated. electrons are injected into the conduction band ofTi02, while the holes are transported t" the counter electrode by diffusion The LIse of dye and wet electrolyte material has associated instability problems which threatens the suitability ofthis type of solar cell for commercia lizauon purposes. The objective of this proposed stud. is to come up with J semiconductor material of a smaller band-gap which can ?e used to fabricate a solar cell. This is to be: achieved by doping the metal oxide (TiO?) with germanium utilizing the property of the semiconductor nanodoi band gap variation with the size. The reduction of the band gap is expected to broaden the wave lengjh range of the incident light that can be absorbed by the material. This involves the use of large band gap materials (TiO],) ill the form of a thin film that acts as the matrix within which atoms of Ge are added bv doping. This enables the tailoring of the band gap of the matrix semiconductor (TiO:,- ') tel absorb incident radiation of a wide range or wavelengths. Film deposition will be done using the spuuering method. Substrate temperatures will be varied for deposition in order to vary the phase. Annealing of the deposited films will be done at different temperatures. The films will then be investigated using various techniques 10 establish their structural. optical, electrical and opto-electr ical properties. The results of the investigation will help to optimize the material performance for fabrication of the solar cells ()fhlgh efficiency and low cost.