Investigation of the π-Spacer through Synthesis and Characterization of Phenothiazine Dyes for Dye-Sensitized Solar Cells

Abstract

The search for new ways of harvesting energy from the sun led to development of dye-sensitized solar cells (DSSC) by O Regan and Grätzel in 1991. These solar cells are built up by a nanoporous semiconductor, a dye that is sensitized onto the aforementioned semiconductor, and an electrolyte acting as a redox shuttle. Calculations performed by Venkatraman et al. at NTNU, present phenothiazine dyes as promising candidates for DSSC. A series of dyes, the MFV2/DMA1-series, has been synthesized where the structure element known as the π-bridge is being varied. The π-bridges influence the region where the dye can absorb light, and the excited dye s ability to inject electrons to the conducting band of the semiconductor. Two novel dyes for DSSC, DMA1-3 and DMA1-4, has been synthesized. Following a five-step synthesis, DMA1-3 was synthesized in a total yield of 31%. The seven-step synthesis of DMA1-4 was performed in a total yield of 20%, the π-bridge building block for this dye was synthesized in a five-step process in yields of 1-4%. The novel dyes DMA1-3 and DMA1-4 were characterized as dyes for DSSC, along with 5 other dyes synthesized previously in the research group by master student Vold and the author. The dye DMA1-1 displayed the best DSSC-performance, with a short-circuit current density of 8.88 mA cm−2 leading to a power conversion efficiency of 3.90% under solar simulation with AM 1.5 G conditions.