The applicability of 4-trimethylsilylpyridine (4TMSpy) was investigated as an organic additive to the electrolyte solution of dye-sensitized solar cells. The N3-sensitized solar cell with 4TMSpy showed higher light-to-electric energy conversion efficiencies than that with the ordinary organic additive of 4-tert-butylpyridine by a factor of ca. 1.1. This improvement of the photovoltaic performance was considered to be due to the bulkiness and peculiar electronic properties of the trimethylsityl group.