Flexible glass substrate based dye sensitized solar cells

Abstract

Dye sensitized solar cells (DSSC) on flexible substrates are ideal for making low-cost PV products available for a wide range of low power applications. In addition to lower material costs, a flexible solar cell also offers economies of scale through high volume roll-to-roll manufacturing. A disadvantage of using flexible polymer substrates, stems from their poor stability and degradation of both electrical and optical qualities when subjected to thermal processing steps required to make high efficiency TiO2 photoelectrodes. This study evaluates the potential of indium doped tin oxide (ITO) coated flexible glass, known as Corning® Willow® Glass, as an alternative to polymer substrates for fabricating flexible DSSCs. The strain point and bend radius of this glass allows it to withstand high sintering temperatures and also makes it potentially suitable for roll-to-roll manufacturing.DSSCs fabricated using a 10µm TiO2 mesoporous layer and sensitized with N719 dye demonstrate that flexible glass DSSCs show a power conversion efficiency of 4.53% compared to the 3.09% efficiency value obtained for DSSCs fabricated using commercially available ITO coated thick glass. The enhanced performance of the Willow Glass DSSC is reflected in the improved fill factors (FF). As expected, cells fabricated with similar procedures using fluorine doped tin oxide (FTO) coated glass substrates yielded a higher power conversion efficiency of 7.42% since its sheet resistance remains substantially lower even after the heat treatment unlike ITO. With FTO, instead of ITO, flexible glass DSSCs could potentially achieve higher efficiencies comparable to standard thicker glass DSSCs. This is expected when suppliers are able to produce FTO coated willow glass with reproducible electrical conductivity.This study demonstrates for the first time that DSSCs can be fabricated using light weight, flexible glass substrates with comparable efficiencies to the standard thicker glass based DSSCs.