May 29, 2012
Highly flexible Ti-mesh upgrades DSSC electrodes
Dye-sensitized solar cells (DSSCs) based on TiO2 nanotubes have been shown to exhibit a better electron collection capability than nanoparticle-based designs due to a faster charge transfer and a lower recombination rate. TiO2 nanotubes can be grown effectively on Ti foil, but the substrate is opaque, which means that DSSCs based on anodic TiO2 nanotubes on Ti foil should be illuminated from the back side, which decreases the amount of light that can be harvested by the device. To avoid the problem, a light-pervious alternative to the Ti foil is required.
One candidate is titanium mesh as the open area of the mesh makes it possible for light to penetrate into the cell, allowing front-side illumination. Reporting their results in the journal Nanotechnology, researchers from Pusan National University, South Korea, and Shanghai Institute of Ceramics, China, have put devices to the test.
The anodic growth of TiO2 nanotubes on a mesh substrate should be carried out at relatively low temperatures compared with growth on a foil substrate. Relatively high growth temperatures give rise to a higher oxidation rate and produce longer nanotubes, but these conditions also speed up the dissolution of the top part of the nanotubes, resulting in a jumbled surface.
In the study, the team compared the conversion efficiencies of DSSCs based on mesh- and foil-type substrates. The results demonstrated the superiority of the mesh-type DSSCs, as the efficiency was found to be two times higher than DSSCs based on a foil-type substrate. What is more, the mesh structure is highly bendable, which allows the solar cell to flex to suit various applications.
The flexible DSSCs featuring titanium mesh as both photoanode and cathode substrates are transparent, lightweight and available in a variety of sizes and shapes.
Full details can be found in the journal Nanotechnology.
About the author
The first author Weizhen He is a PhD student in the Department of Nano Fusion Technology at Pusan National University in Korea. Prof. Yoon-Hwae Hwang is her thesis advisor and Prof. Hyung-Kook Kim is her thesis co-advisor. This work was carried out in the Nanosystems Lab (SRIN). The assembly of solar cells and efficiency measurement was performed with the help of Dr Jijun Qiu and Dr Fuwei Zhuge who worked in Prof. Xiaomin Li’s research group at the Shanghai Institute of Ceramics, Chinese Academy of Sciences. The work was supported by the NRF in Korea through the collaboration with Prof. Jae-Ho Lee at Hongik University and Prof. Yang-Do Kim at Pusan National University.