Improved performance of dye-sensitized solar cells with dye coating method and co-adsorbant

Abstract

Dye-sensitized solar cells (DSSCs) are one of the strong alternatives to conventional Si-based solar cells due to the advantages such as transparency, various colors and comparable efficiency to that of an amorphous Si solar cell. DSSC research also has been broadened to many applications such as flexible devices, module with large size, windows with transparency in need. The possible low cost for fabrication is another advantage. Since the discovery, researchers have focused more on improving the efficiency of the cells rather than their productivity. Productivity is the important factors in lowering the manufacturing costs. In DSSC production, dye coating is one of the important factors in the fabrication process. Ru-based dye adsorption on a photo anode takes a long time. To maximize energy harvesting of DSSCs, many researchers approaching to make lower the manufacturing cost, which could take a short time to adsorb the dye on a TiO2 nanocrystalline surface. Here, I present the prominent way to fabricate a cell with fast dye coating method. Applied solvents are from mono alcohol to triols with various temperatures and concentrations of the dye. According to experiments, dye coating time can be shortened down from several hours to 3 min. To compare the new system to the conventional system, various analysis tools were applied for further investigation. The new solvent system with ethylene glycol, gives many advantages such as saving solvent usage, short coating time, and easy procedure for mass fabrication. However, I have a problem to make cells by dye aggregation at that time. Therefore, I report a method that can solve this problem. I could success to coat dye to use the solvent mixture without dye degradation. The proposed solvent system for dye coating results in fast dye coating with less concerns of dye degradation even at high temperatures, and is convenient for preparing double dye-coating layers on the working electrode. The solvents were ethylene glycol (EG) and glycerol (Gly). Because part of the mixture delivers dyes to the TiO2 surface whereas most of the highly viscous solvent stays on the top part of the TiO2 film. Also, the viscous solvent system could control coating depth with these solvents. So, I could make to apply the double-dye-layer electrode with N719 and N749 dyes. Furthermore, I also present a one of the methods used to improve DSSC performance with representative Ru-based dyes such as N7, N719 is the addition of a co-adsorbant in the dye solution. The working mechanism of these co-adsorbants is mainly by formation of a blocking layer on dye-empty spaces on TiO2 nanoparticles. This blocking agent effectively prevents back electron transfer. As a result, DSSCs with titanate co-adsorbant showed significantly increased energy conversion efficiency.