Novel uses of TiO₂ in crystalline silicon solar cells

Novel applications for titanium dioxide (TiO₂) thin films have the potential to reduce production costs of silicon (Si) solar cells, especially for structures like the buried-contact solar cell. This paper demonstrates several new uses for TiO₂ films. Firstly, it is demonstrated that the TiO₂ film does not contaminate the silicon wafer or furnace after lengthy high-temperature processing. Secondly, a thin silicon dioxide passivation layer can be grown at the TiO₂/Si interface by performing a brief oxidation after the deposition of the TiO₂. With this method, very low emitter dark saturation currents have been achieved on lightly-diffused high-resistivity float zone wafers. Thirdly, TiO₂ films doped with 1% phosphorus were investigated as an emitter dopant source. Initial results have shown that light diffusions are possible. Finally, the applicability of TiO₂ as a phosphorus diffusion barrier was investigated.