SnO2 nanorods arrays functionalized TiO2 nanoparticles based UV photodetector with high and fast response

TiO2 nanoparticles (NPs) based ultraviolet (UV) photodetectors (PDs) present extremely slow response duo to the low electron mobility of TiO2 (similar to 0.1 to 1.0 cm(2) V-1 S-1) and electron loss in conspicuous interspace among the TiO2 NPs. In this work, SnO2 nanorods (NRs) arrays with high electron mobility are proposed to improve electron transfer in TiO2 NPs by the highly oriented structure. Double layers of TiO2 NPs are deposited on the SnO2 NRs arrays by TiCl4 hydrolysis reaction. The top layer is consisted of TiO2 NPs clusters, which contributes to large UV light harvest and ensures high photoresponsivity. And the bottom layer of small TiO2 NPs are distributed on and into SnO2 NRs array, forming heterojunction between them, which favors for quick electrons transmit and ensures fast response rate. In contrast to most reported UV PDs based on other TiO2 nanostructures, the present SnO2 NRs arrays/TiO2 NPs based UV PDs simultaneously exhibit a short response time and a high photoresponsivity, which are less than 0.2 s (rise and decay time) and 21.6 A W-1, respectively. This response rate is almost one order of magnitude faster than that of pure-TiO2 NPs, while the responsivity still remains much higher than the commercial values (0.1-0.2 A W-1). The superior performance is ascribed to the large UV light harvest offered from the layer of TiO2 NPs clusters, the directional electron transmission channel provided by SnO2 NRs arrays and improved electrons transmit by heterojunctions formed between SnO2 and TiO2. Moreover, the present UV PDs with excellent UV light selectivity and fabulous detection sensitivity are competitive and highly applicable in UV detection.