Photoelectrochemical characterisation and optimisation of electrodeposited ZnO thin films sensitised by porphyrins and phthalocyanines

Abstract

Hybrid thin films of crystalline ZnO modified by 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrinato zinc (TSTPPZn) and 2,9,16,23-tetrasulfophthalocyaninatozinc(II) (TSPcZn) were prepared by electrochemical deposition from aqueous zinc salt solutions. A "one-step" process with the sensitisers adsorbed during ZnO deposition represented the most simple approach. ZnO was also grown independently in the presence of Eosin Y as a structure-directing agent, which was then removed and the sensitisers were chemisorbed from solutions ("readsorption" method). The photoelectrochemical characteristics of the electrodes were studied by photocurrent spectra and by time-resolved photocurrent measurements in an acetonitrile-based solution containing I3(-)/I(-) as the redox electrolyte. In films with both sensitisers present, both sensitisers worked in parallel providing panchromatic sensitisation. Recombination of electrons injected into the conduction band of ZnO with remaining holes in the HOMO of the sensitisers was indicated for the one-step films, but was considerably suppressed for the films prepared by the readsorption method. Films prepared by the readsorption method showed a significantly increased efficiency by an increased surface area and suppressed recombination.

Nanoparticulate Dye-Semiconductor Hybrid Materials Formed by Electrochemical Self-Assembly as Electrodes in Photoelectrochemical Cells

“…2). This could also be seen in a maximum IPCE = 10% (TSTPP) and IPCE = 12% (TSPcZn) for the twostep films as opposed to IPCE = 0.14% (TSTPP) and IPCE = 0.6% (TSPcZn) for the one-step films [18]. It is interesting to note that in these cases the ZnO film thickness and even the dye load or dye concentration could be quite similar (Table 2) and still gave significantly better performance for the films prepared by the two-step method, also seen in a clearly increased photocurrent when normalized to the amount of sensitizers in the films ( Table 2).…”

Electrodeposited Porous ZnO Sensitized by Organic Dyes – Promising Materials for Dye‐Sensitized Solar Cells with Potential Application in Large‐Scale Photovoltaics

“…The presence of the porphyrin stabilized the phthalocyanine on the ZnO since a greater amount of TSPcZn was adsorbed. In the photosensitization of ZnO, TSPcZn and TSTPPZn worked in parallel using light in their respective absorption range [259] . The presence of TSPcZn led to a threefold increase of the photoelectrochemical quantum effi ciency of TSTPPZn [259] .…”

“…In the photosensitization of ZnO, TSPcZn and TSTPPZn worked in parallel using light in their respective absorption range [259] . The presence of TSPcZn led to a threefold increase of the photoelectrochemical quantum effi ciency of TSTPPZn [259] . An increased rate constant of electron transfer to oxidized TSPcZn (regeneration reaction) suppressed the competing recombination via TSTPPZn and TSPcZn took over a role as charge mediator in the regeneration reaction of oxidized TSTPPZn.…”

Fabrication of ZnO Nanorods by Atmospheric-Pressure Solid-Source CVD Using Ethanol-Assisted Low-Temperature Vaporization

“…ZnO nanorods (NRs) have potential application in solar cells 1,2 , chemical 3 and ultraviolet 4 sensors and piezoelectronic devices 5 in small scales. There have been many reports regarding methods to fabricate ZnO NRs and devices using them.…”