Application of a novel microwave plasma treatment for the sintering of nickel oxide coatings for use in dye-sensitized solar cells

Abstract

In this study the use of microwave plasma sintering of nickel oxide (NiO x ) particles for use as ptype photoelectrode coatings in dye-sensitized solar cells (DSSCs) is investigated. NiO x was chosen as the photocathode for this application due to its stability, wide band gap and p-type 2 nature. For high light conversion efficiency DSSCs require a mesoporous structure exhibiting a high surface area. This can be achieved by sintering particles of NiO x onto a conductive substrate. In this study the use of both 2.45 GHz microwave plasma and conventional furnace sintering were compared for the sintering of the NiO x particles. Coatings 1 to 2.5 µm thick were obtained from the sintered particles (mean particle size of 50 nm) on 3 mm thick fluorine-doped tin oxide (FTO) coated glass substrates. Both the furnace and microwave plasma sintering treatments were carried out at ~450 ºC over a 5 minute period. Dye sensitization was carried out using Erythrosin B and the UV-vis absorption spectra of the NiO x coatings were compared. A 44% increase in the level of dye adsorption was obtained for the microwave plasma sintered samples as compared to that obtained through furnace treatments. While the photovoltaic performance of the DSSC fabricated using the microwave plasma treated NiO x coatings exhibited a tenfold increase in the conversion efficiency in comparison to the furnace treated samples. This enhanced performance was associated with the difference in the mesoporous structure of the sintered NiO x coatings.

Electrochemical characterization of NiO electrodes deposited via a scalable powder microblasting technique

“…41 This issue is under further investigation. To benchmark the NiO x coatings prepared via the microblast technique (Sample A), we have also prepared NiO x films through the sintering 22 of spray deposited layers (Sample B) of NiO x nanoparticles on Ni sheets. Both microblast and nanoparticulate NiO x coatings have thickness values in the range of ~1.2 µm.…”

“…43,44 In order to compare the properties of the NiO x coatings prepared by the microblasting technique,(Sample A), NiO x nanoparticulate coatings were also deposited using conventional powder spraying and sintering (Sample B). 22 In this method NiO x nanoparticles were deposited onto 0.15 mm thick nickel sheets (2 cm x 2 cm) using a spraying technique similar to that described previously by Halme et al. 46 NiO x nanoparticles, with an average particle size of 50 nm (Sigma-Aldrich) were suspended in 2-propanol (20 mg/mL), and a loosely adherent particulate layer of NiO x coatings was spray-deposited onto a Ni sheet.…”

“…5 Because of this interesting combination of electrical and optical properties, NiO x has been considered for energy storage applications, [6][7][8] in electrochromic devices as transparent electrode, 9-17 in optoelectronic devices as electron barrier, 18,19 for gas sensing, 20,21 and, more recently, in dye-sensitized solar cells (DSCs) as photoactive cathode. [22][23][24][25][26][27][28][29][30][31][32][33][34][35] The utilization of NiO x in such diverse applications has been accompanied by the development of various preparation methods and deposition techniques, aimed at producing NiO x -based materials with variable chemical composition, electrical resistivity, compactness and morphology. Examples include electrochemical deposition, 36 chemical vapor 37 and bath deposition, 38 spray pyrolysis, 39,40 sol-gel method, 14,23,25,41 hydrothermal synthesis, 29,42 and sputtering.…”

“…45 To our knowledge, this is the first study that investigates the potential of the microblast technique for the deposition of metal oxide coatings for photoelectrochemical purposes. The morphological, structural, compositional, electrochemical and photo-electrochemical characteristics of microblast NiO x samples are described and compared with those of NiO x nanoparticulate layers prepared by furnace sintering, 22 and with those of nanocrystalline NiO x films prepared via sol-gel methods as reported in the literature. 9b,12b,14b,15b Specifically the objective of this work is to evaluate the photo-electrochemical performance of microblast NiO x coatings in the bare state and in the sensitized version with the dye Erythrosin B (ERY).…”

Achieving enhanced DSSC performance by microwave plasma incorporation of carbon into TiO2 photoelectrodes

“…Methane has been widely reported as a precursor for the plasma deposition of diamond and graphitic films [14][15][16]. Microwave (MW) plasmas have also been used previously for the sintering of metal oxide nanoparticles such as NiO x and TiO 2 for use in solar devices [17,18].…”