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

• 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.

Ämnesord

NATURVETENSKAP  -- Kemi -- Annan kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Other Chemistry Topics (hsv//eng)

Nyckelord

Excited-state electron transfer

Ru(bpy)(3)

DSSCs

Photochemistry

Solid state

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