Journal Article

Switched photocurrent direction in Au/TiO2 bilayer thin films

Liu, Gang, Chen, Hongjun, Wang, Lianzhou

2015

Overview

Switched photocurrent direction in photoelectrodes is a very interesting phenomenon and has demonstrated their potentials in important applications including photodiodes, phototransistors, light-driven sensors and biosensors. However, the design and mechanism understanding of such photoelectrodes remain challenging to date. Here we report a new phenomenon of sequence-driven the photocurrent direction on a simple bilayer structure of 5 nm thick Au and 10 nm TiO 2 under visible-light irradiation. It is found that when Au layer are deposited as the outer layer on TiO 2 coated fluorine doped tin oxide (FTO) substrate (designated as FTO/TiO 2 /Au), anodic photocurrent is obtained due to the band bending formed at the electrode-electrolyte interface. Interestingly, simply swapping the deposition sequence of Au and TiO 2 leads to cathodic photocurrent on FTO/Au/TiO 2 electrode. Characterization and calculations on the photoelectrode reveals that the photogenerated electrons can be easily trapped in the energy well formed between the band bending and the Schottky contact, which allows electronic tunnelling through the 1.6 nm thick space charge layer, resulting in a unique anodic to cathodic photocurrent conversion. The understanding of this new phenomenon can be important for designing new generation optoelectronic converting devices in a low-cost and facile manner.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/301/299/890 / 639/925/357/995 / Biosensors / Electrodes / Energy / Humanities and Social Sciences / Irradiation / Light / multidisciplinary / Photocatalysis / Radiation / Science / Spectrum analysis / Thin films / Tin / Tin oxide / Titanium dioxide