Nitrogen-containing heterocyclic compounds were investigated as electrolyte solvents of dye-sensitized solar cells. 3-Methyl-2-oxazolidone (NMO) was revealed to exhibit the highest efficiency (7.0%) among the five solvents. The conversion efficiency of 1-methyl-2-pyrrolidone (NMP), which has the lowest melting point, was improved from 5.0 to 6.5% by adding the high relative permittivity solvent of N-methylformamide with volume ratio 1:1.
