Excited-State Dynamics of [Ru(bpy)3]2+ Thin Films on Sensitized TiO2 and ZrO2 |
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| Authors: | Dr. Valentina Leandri Dr. Peng Liu Dr. Azar Sadollahkhani Dr. Majid Safdari Prof. Lars Kloo Prof. James M. Gardner |
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| Affiliation: | Department: Department of Chemistry Division of Applied Physical Chemistry, KTH Royal Institute of Technology, Teknikringen 30, SE-10044 Stockholm, Sweden |
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| 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. |
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| Keywords: | Excited-state electron transfer Ru(bpy)3 DSSCs Photochemistry Solid state |
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