Excited‐State Dynamics of Ru(bpy)32+ Thin Films on Sensitized TiO2 and ZrO2

摘要

The excited state dynamics of Tris(2,2′‐bipyridine)ruthenium(II) hexafluorophosphate, [Ru(bpy)3(PF6)2], was investigated on the surface of bare and sensitized TiO2 and ZrO2 films. The organic dyes LEG4 and MKA253 were selected as sensitizers. A Stern–Volmer plot of LEG4‐sensitized TiO2 substrates with a spin‐coated [Ru(bpy)3(PF6)2] layer on top shows considerable quenching of the emission of the latter. Interestingly, time‐resolved emission spectroscopy reveals the presence of a fast‐decay time component (25±5 ns), which is absent when the anatase TiO2 semiconductor is replaced by ZrO2. It should be specified that the positive redox potential of the ruthenium complex prevents electron transfer from the [Ru(bpy)3(PF6)2] ground state into the oxidized sensitizer. Therefore, we speculate that the fast‐decay time component observed stems from excited‐state electron transfer from [Ru(bpy)3(PF6)₂] to the oxidized sensitizer. Solid‐state dye sensitized solar cells (ssDSSCs) employing MKA253 and LEG4 dyes, with [Ru(bpy)₃(PF₆)₂] as a hole‐transporting material (HTM), exhibit 1.2 % and 1.1 % power conversion efficiency, respectively. This result illustrates the possibility of the hypothesized excited‐state electron transfer.