Low-Temperature Fabrication of Platinum Nanostructures and Novel Platinum/Graphene Nanocomposites for Dye-Sensitized Solar Cells

• Main Authors: Wu, Hsin-Hui, 吳忻蕙
• Other Authors: Eric Wei-Guang Diau
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/92699074998954468881

碩士 === 國立交通大學 === 應用化學系分子科學碩博士班 === 100 === Polyol synthesis is a successful method to generate metal nanostructures with well defined and controllable shapes. Here we report the fabrication of Pt nanostructures as transparent counter electrode (CE) for dye-sensitized solar cells (DSSC) via a dip-coating process suitable for flexible devices. A self-assembled monolayer (SAM) of Pt nanostructures was fabricated by linking Pt nanoparticles with thio functionalized transparent conducting oxide (TCO) substrate. Scanning electron microscope (SEM) top-view images show the Pt nanoparticles homogeneously distributed on the surface of a fluorine doped tin oxide (FTO) conductive glass. Ttransmission electron microscopic (TEM) cross-section images reveal that the Pt nanopaticles are highly crystalline and self-organized on the substrate with a uniform size of 2 nm in diameter. The DSSC device made of SAM CE and optimized TiO2 photoanode attained an overall power conversion efficiency 9.2% on indium tin oxide (ITO) substrate, which is slightly higher than the device with a conventional thermal cluster Pt (TCP-Pt) CE on FTO substrate (9.1%) ；the device made of SAM CE on FTO substrate gives the efficiency 9.0%. As second part of this thesis, a novel structure of Pt/Graphene nano-composite was developed as CE materials for DSSC applications. Using cyclic electro-deposition (CED) approach previously developed in this laboratory, Pt nanostructures were deposited uniformly on a graphene thin film, dispersed on the surface of FTO substrate. Post-treatments of graphene nanosheets to increase the amount of oxygen-containing functional groups and the defect sites were performed to improve the catalytic activity. In our study, the device incorporating Pt-grafted graphene CE showed a power conversion efficiency 8.0%, which is slightly higher than that of a device made of conventional TCP-Pt CE (7.9%), due to an improvement of FF. The CEs made of Pt/Graphene composite are superior to other electrodes that consist solely of graphene or Pt films. Based on the results obtained from the impedance spectral measurements, the charge transfer resistance of Pt/Graphene CE is 1.8 Ω, which is smaller than that of TCP-Pt CE (3.5Ω) and that of graphene CE (23KΩ). Our results indicate that the Pt/Graphene composite materials have excellent electro-catalytic performance, perfectly suitable for use as CE for DSSC.