Article pubs.acs.org/JPCC
High Photoconductive Response of Gas-Sensitized Porous Nanocrystalline TiO2 Film in Formaldehyde Ambience and Carrier Transport Kinetics Shasha Zhang, Changsheng Xie,* Zhijun Zou, Li Yang, Huayao Li, and Shunping Zhang State Key Laboratory of Material Processing and Die & Mould Technology, Nanomaterials and Smart Sensors Research Laboratory, Department of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, P. R. China S Supporting Information *
ABSTRACT: We propose a gas-sensitized porous nanocrystalline TiO2 film with a potential application in photovoltaic devices and report about the systematic photoconductivity study of it. The quantitative results show that the gas-sensitized TiO2 film in formaldehyde atmosphere exhibits much higher photoconductivity (3−4 orders of magnitude) and longer carrier lifetime than usual. The intriguing performance of the gas-sensitized TiO2 film indicates the distinct charge carrier transport kinetic courses, whose contributions to the photoconductivity are shown in a designed flowchart. From the flowchart, it is clearly found that two electron loss processes, recombination and electron scavenging, are suppressed for the gassensitized TiO2 film in formaldehyde gas, leading to large improvements of photoconductivity and carrier lifetime. The results provide the potential of improving efficiency of photovoltaic devices, and measuring photoconductivity under target gas appears to be a useful tool for research on photocatalytic and photoelectrical processes.
1. INTRODUCTION Titanium dioxide, TiO2, is currently considered as the most promising material of photoelectric conversion devices due to its chemical inertness, photostability, nontoxicity, and low cost.1 The main limits of TiO2 in these applications are the wide band gap (around 3.2 eV), which permits the response to only a small fraction of the solar spectrum (
