Enhanced photoelectrochemical performance of Si/TiO2 with a high atomic density SiO2 buffer layer

Abstract

Nanostructured Si is a promising material for photoelectrochemical water splitting, but it has the problem of being well oxidized in water. Depositing a TiO2 layer on the Si surface is an effective way to protect it from oxidation and increase light absorption. However, the lattice mismatch between Si and TiO2 acts as a defect that causes an efficiency reduction. To improve the interface and electrical properties of TiO2/Si, nitric acid oxidation of Si (NAOS) is used to form a high-density SiO2 layer and analyze the effect of photoelectrochemical properties. Due to the lattice mismatch, the TiO2/Si sample (−3.12 mA/cm2) decreases about 1.8 times when using SiO2. In TiO2/SiO2/Si samples (-5.70 mA/cm2) further decrease after post-oxidation annealing (POA) (−7.70 mA/cm2). As a result, it can be seen that by fabricating an ultra-thin high-density SiO2 layer, the lattice mismatch at the TiO2/Si interface is reduced and the photocurrent density is improved.