Synthesis and characterization of novel cyclometalated iridium(III) complexes for nanocrystalline TiO 2-based dye-sensitized solar cells

Abstract

Four novel cyclometalated iridium(III) complexes with the following general formulas were synthesized and characterized using 1H NMR, { 1H– 1H} COSY, ESI-MS spectral and elemental analysis data: [Ir(C ∧N ∧C)(ptpy-COOH)] + (C ∧N ∧C = 2,6-diphenylpyridinato ( 1); 2,4,6-triphenylpyridinato ( 2), ptpy-COOH = 4′-(4-carboxyphenyl)-2,2′:6′,2“-terpyridine) and [Ir(C ∧N ∧C)(tpy-COOH)] + (C ∧N ∧C = 2,6-diphenylpyridinato ( 3); 2,6-ditolylpyridinato ( 4), tpy-COOH = 4′-carboxy-2,2′:6′,2″-terpyridine). The photophysical and redox properties and photovoltaic performance of the Ir(III) complexes as photosensitizers in nanocrystalline TiO 2-based solar cells were studied and compared to those of cis-diisothiocyanatobis(4,4′-dicarboxy-2,2′-bipyridine)ruthenium(II) ( N3). Dye 4 exhibits the highest photovoltaic performance with an overall solar energy conversion efficiency of 2.16%.