title: Optimization of dye adsorption time and film thickness for efficient ZnO dye-sensitized solar cells with high at-rest stability.
abstract: Photoelectrodes for dye-sensitized solar cells were fabricated using commercially available zinc oxide (ZnO) nanoparticles and sensitized with the dye N719. This study systematically investigates the effects of two fabrication factors: the ZnO film thickness and the dye adsorption time. Results show that these two fabrication factors must be optimized simultaneously to obtain efficient ZnO/N719-based cells. Different film thicknesses require different dye adsorption times for optimal cell performance. This is because a prolonged dye adsorption time leads to a significant deterioration in cell performance. This is contrary to what is normally observed for titanium dioxide-based cells. The highest overall power conversion efficiency obtained in this study was 5.61%, which was achieved by 26-μm-thick photoelectrodes sensitized in a dye solution for 2 h. In addition, the best-performing cell demonstrated remarkable at-rest stability despite the use of a liquid electrolyte. Approximately 70% of the initial efficiency remained after more than 1 year of room-temperature storage in the dark. To better understand how dye adsorption time affects electron transport properties, this study also investigated cells based on 26-μm-thick films using electrochemical impedance spectroscopy (EIS). The EIS results show good agreement with the measured device performance parameters.
authors.affiliation: Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei, 10608, Taiwan. wanchin@ntut.edu.tw.
authors.forename: Wei-Chen
authors.initials: WC
authors.lastname: Chang
authors.forename: Chia-Hua
authors.initials: CH
authors.lastname: Lee
authors.forename: Wan-Chin
authors.initials: WC
authors.lastname: Yu
authors.forename: Chun-Min
authors.initials: CM
authors.lastname: Lin