Charge Recombination Deceleration by Lateral Transfer of Electrons in Dye-Sensitized NiO Photocathode

• Control of charge separation and recombination is criticalfordye-sensitized solar cells and photoelectrochemical cells, and forp-type cells, the latter process limits their photovoltaic performance.We speculated that the lateral electron hopping between dyes on ap-type semiconductor surface can effectively separate electrons andholes in space and retard recombination. Thus, device designs wherelateral electron hopping is promoted can lead to enhanced cell performance.Herein, we present an indirect proof by involving a second dye tomonitor the effect of electron hopping after hole injection into thesemiconductor. In mesoporous NiO films sensitized with peryleneimide(PMI) or naphthalene diimide (NDI) dyes, dye excitation led to ultrafasthole injection into NiO from either excited PMI* (tau < 200fs) or NDI* (tau = 1.2 ps). In cosensitized films, surface electrontransfer from PMI- to NDI was rapid (tau = 24ps). Interestingly, the subsequent charge recombination (ps-mu s)with NiO holes was much slower when NDI- was generatedby electron transfer from PMI- than when NDI wasexcited directly. We therefore indicate that the charge recombinationis slowed down after the charge hopping from the original PMI sitesto the NDI sites. The experimental results supported our hypothesisand revealed important information on the charge carrier kineticsfor the dye-sensitized NiO photoelectrode system.

Ämnesord

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

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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