High efficiency photovoltaic cells based on metal substrate and nano structured TiO₂ films

Abstract

Dye-sensitized solar cell (DSSC) has been nominated as a promising solution to the future energy and environmental problems since its beginning by O’Regan and Gr$\ddot{a}$tzel due to its low fabrication cost, eco-friendly characteristics and reasonable photon-to-electron conversion efficiency (> 11%). However, relatively low conversion efficiency of the DSSC, compared with the crystalline Si (24.7%) or thin film CIGS (19.9%), restricts its further applications so far. In order to improve the conversion efficiency of the DSSC, continuous attempts have been made in the past decades. Researchers have concentrated their attention on the working or counter electrode materials, synthesizing dye, additives of the electrolytes, nano-structures for enhancing light scattering and so on. However, there have been few reports on the interface between nano-crystalline electrode material and current collecting substrates, in particular on the DSSC with thin and light-weight metal substrates. A DSSC with thin and lightweight substrate would have a greatly expanded degree of utility. However, widely used conductive-layer-coated plastic films degrade at the $TiO_2$ sintering temperature of approximately 500℃. In addition, sintering of $TiO_2$ particles below the plastic-degeneration temperature causes poor necking of $TiO_2$ particles. In order to fabricate a nano-porous $TiO_2$ electrode on a conductive-layer-coated plastic film, several low-temperature processes have been proposed, such as hydrothermal crystallization, electrophoretic deposition, and low-temperature sintering. However, these methods result in poor electrical contact between nano-porous particles and conductive substrates. Instead of conductive-layer-coated plastic films, metal substrates were proposed. Metal substrates are excellent alternatives to conductive layer coated plastic films, because they do not require a limitation of the sintering temperature. In this work, focusing on the characteristics of the ...