Electrochemical Characteristics of Multi-walled Carbon Nanotubes Films in the Iodide/Tri-iodide Redox System

• Main Authors: Chia-Jung Chang, 張嘉容
• Other Authors: Wen-Tuan Wu
• Format: Others
• Language: zh-TW
• Published: 100
• Online Access: http://ndltd.ncl.edu.tw/handle/61352807634983031857

碩士 === 南台科技大學 === 光電工程系 === 99 === In order to search for an efficient and low cost counter electrode in a DSSC. In recent years, the focus of development was replaced the platinum by the carbon, therefore the CNT were grown on P+-Si wafer using an electron cyclotron resonance chemical vapor deposition(ECR-CVD). The methane as the carbon source and Ni as catalyst can synthesize carbon nanotubes. To find the best conditions for growth of carbon nanotubes, the process parameters include the thickness of nickel catalyst, pretreatment time and the process pressure. The CNT was used to explore the performance of the counter electrode in DSSC. The correlation between the CNTs morphologies and the charge transfer resistance was also investigated. In this study, the CNT counter electrode was prepared by ECR-CVD at low temperature of 500℃.The morphologies and microstructures of CNTs were investigated by scanning electron microscopy (SEM). The charge-transfer resistance(RCT) was examined by autolab potentiostat. The results showed that the best RCT of CNTs grown at low pressure of 1.2×10-3 torr were estimated to be 2.65Ω-cm2、1.41Ω-cm2 and 14.8Ω-cm2 for 1.5nm-thick, 3nm-thick and 4.5 nm-thick catalyst film, respectively. The density of CNTs grown on 1.5nm nickel catalyst was higher than 3nm nickel catalyst that affected the diffusion of iodine electrolyte. For the CNTs grown on 4.5 nm-thick catalyst film were coved a thin carbon layer, which may lower the electrode. The CNT counter electrodes grown at pressure of 1.2×10-2 torr on 4.5 nm-thick catalyst film have a large average surface roughness, and a good chemical stability to I3-/I- couple. A low charge transfer impedance (RCT) of approximately 4.03Ω-cm2 can be obtained for an electrode area of 0.16cm2.