Effect of regioisomeric substitution patterns on the performance of quinoxaline-based dye-sensitized solar cells

Abstract

Regioisomeric quinoxaline-based dyes (NQXs) were synthesized to study the effect of substitution patterns on the performance of quinoxaline-based dye sensitized solar cells (DSSCs). The H-1 NMR results indicated that the substitution patterns of ethylene groups on the quinoxaline unit greatly affect the molecular architecture through C-H center dot center dot center dot N hydrogen bonding, which also influenced the absorption and efficiency of the DSSCs. The highest occupied molecular orbital (HOMO) levels of the NQXs were estimated to range from 0.94 to 0.99 V by cyclic voltammetry and visible absorption studies, which is suitable for DSSCs. The photocurrent density-voltage curves and incident photon-to-electron conversion efficiency spectra of NQXs indicated that the introduction of phenothiazine groups at the 2-and 3-positions of quinoxaline is the most effective pattern for quinoxaline-based organic sensitizers in DSSCs.