Dye-sensitized solar cells containing plasma jet deposited hierarchically nanostructured TiO2 thin photoanodes

Abstract

The investigation of dye-sensitized solar cells (DSCs) using a very thin (0.8 to 4.7 mm) transparent photoanode based on a hierarchically nanostructured TiO 2 film prepared via Plasma Assisted Supersonic Jet Deposition (PA-SJD), in combination with the DSC benchmark photosensitizer N719, is presented. The cell photovoltages (nearly 0.8 V) and the amount of adsorbed dye and photocurrent densities, normalized over the film thickness, are higher than those of DSCs prepared with thicker (9 mm) conventional screen-printed TiO 2 films. A record efficiency value of 5.7% (standard AM 1.5G solar irradiation) for very thin nanostructured titania photoanodes is obtained with a 2 mm PA-SJD TiO 2 film.Electrochemical impedance spectroscopy shows that PA-SJD devices are endowed with higher charge recombination resistance (lower recombination losses) and electron lifetimes compared to conventional nanocrystalline films.

Controlled Deposition of Nanostructured Hierarchical TiO2 Thin Films by Low Pressure Supersonic Plasma Jets

“…Specifically, the deposition rate can be varied, from few tens nm/min to more than 300 nm/min, depending on the substrate position from the nozzle. The deposition rates can widely vary between some tens of nm/min up to tens of µm/min as a function of the precursor flows controlled by the heating temperature, allowing one to use the technology for different purposes [ 33 , 36 ].…”

“…In Figure 6 e,f, the cross-section of the annealed film, deposited at R = 10, shows an increase in the transversal direction, that is, the tree-like hierarchical assembly fanned out. The size of nanoclusters was of the order of 10 nm, and their tree structure could be better visualized by a TEM analysis [ 36 ]. The latter showed the formation of a zig-zag-like structure composed of single, mostly crystalline, domains of 10 nm in size.…”

“…Films of TiO 2 with this hierarchical structural morphology are characterized by a large surface area and have been fabricated as photocathode for photovoltaic applications [ 36 ]. In fact, it has been demonstrated that high-surface-area nanostructures enhance sunlight and dye absorption in specifically designed solar cells, known as dye-sensitized solar cells, and ordered nanostructured networks offer a more direct charge transport pathway that improves the same electron mobility.…”

“…Importantly, when using supersonic jet deposition, new types of sintering processes may emerge during deposition at or close to room temperature [ 34 ]. These features, coupled with the strong adsorption and electrical surface properties of thus-fabricated hierarchical nano-assemblies, make this process suitable for many technological applications [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

The Interaction of a Supersonic Plasma Jet Containing Nanoparticles With a Substrate

“…The growth ofthin and ultra-thin films may be achieved using a large variety oftechniques such as chemical vapour deposition, RF sputtering, pulsedlaser deposition or plasma enhanced chemical vapour deposition [1][2][3]. Recently, a new process, which uses aplasma torch operating at low pressure has been developed with theaim of depositing uniform thin layers on large surfaces [4,5]. In this plasma spraying process plasma jets areused as a heat sources to melt and accelerate the injected nanoparticles which subsequently impinge and solidify on a substrate.…”