Excited-State Dynamics of [Ru(bpy)₃ ]²⁺ Thin Films on Sensitized TiO₂ and ZrO₂.

ABSTRACT: 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.

SUBMITTER: Leandri V 

PROVIDER: S-EPMC6593980 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature