Photoactive thin silver films by atmospheric pressure CVD

We report the visible and UV activity of thin silver films. The films are grown using a CVD process employing aqueous-based silver precursors, flame-assisted chemical vapour deposition. This approach overcomes many of the previously encountered limitations to silver deposition by employing an atmospheric pressure process, low-cost and low-toxicity precursors. The resultant films are assessed for activity using stearic acid destruction as a model compound. We also report on the addition of titania to these silver films to increase the potential functionality. This activity is also demonstrated, where the films appear largely transparent to the eye, further widening the potential application of this work. It is speculated that the nanoparticulate nature, of the CVD silver, is crucial in determining photoactivity

Optically tuned and large-grained bromine doped CH3NH3PbI3 perovskite thin films via aerosol-assisted chemical vapour deposition

Herein, doping of methylammonium lead iodide perovskite thin films with bromine ions is successfully performed for the first time using the aerosol-assisted chemical vapour deposition process. Depending on the doping levels, photoluminescence spectra are shifted relative to their bandgap values. Detailed analysis of scanning electron microscope images showed that increasing the bromine levels linearly increased the grain sizes. The unchanged amount of detected lead provided evidence for the controlled processing conditions. Both bulk and surface compositional techniques confirmed the deposition of marginally iodine rich perovskite thin films

Biocidal silver and silver/titania composite films grown by chemical vapour deposition

This paper describes the growth and testing of highly active biocidal films based on photocatalytically active films of TiO2, grownby thermal CVD, functionally and structurallymodified by deposition of nanostructured silver via a novel flame assisted combination CVD process. The resulting composite films are shown to be highly durable, highly photocatalytically active and are also shown to possess strong antibacterial behaviour. The deposition control, arising from the described approach, offers the potential to control the film nanostructure, which is proposed to be crucial in determining the photo and bioactivity of the combined film structure, and the transparency of the composite films. Furthermore, we show that the resultant films are active to a range of organisms, including Gram-negative and Gram-positive bacteria, and viruses. The very high-biocidal activity is above that expected from the concentrations of silver present, and this is discussed in terms of nanostructure of the titania/silver surface. These properties are especially significant when combined with the well-known durability of CVD deposited thin films, offering new opportunities for enhanced application in areas where biocidal surface functionality is sought

Highly bioactive silver and silver/titania composite films grown by chemical vapour deposition

This paper describes how photocatalytically active films of TiO2, grown by thermal CVD, may be functionally and structurally modified by deposition of nano-structured silver via a novel flame assisted CVD process. The resulting composite films are shown to be highly durable, highly photocatalytically active and are also shown to possess strong antibacterial behaviour. The deposition control, arising from the described approach, offers the potential to control the film nanostructure, which is proposed to be crucial in determining the photo and bio-activity of the combined film structure, and the transparency of the composite films. Furthermore, we show that the resultant films also exhibit “self-regeneration” capability, in that they both kill bacteria present on the film surface and then photo-degrade the residues. Such a dual action significantly reducing the problems of surface deactivation due to build up of contamination. These properties are especially significant when combined with the well-known durability of CVD deposited thin films, offering new opportunities for enhanced application in areas where bioactive surface functionality is sought

Improved FTO/NiOx interfaces for inverted planar triple cation perovskite solar cells

Front electrodes of fluorine doped tin oxide (FTO) thin films and hole transporting layers of nickel oxide thin films have been combined to fabricate 1.063 cm2 inverted planar solar cells with cesium-containing triple cation perovskites as absorber layers. Using atmospheric pressure chemical vapor deposition FTO layers were obtained with low sheet resistance, decreased root mean squareroughness, increased transmission,and reduced optical haze values compared to a widely used commercial FTO substrate. Cell performance outperformed the equivalent cells fabricated using the commercial FTO. With full illumination under maximumpowerpoint tracking, a stabilized power conversion efficiency of 13.78 % was obtained for the champion device

Photocatalytic antimicrobial activity of thin surface films of TiO2, CuO and TiO2 /CuO dual layers on Escherichia coli and bacteriophage T4

TiO2 coated surfaces are increasingly studied for their ability to inactivate microorganisms. The activity of glass coated with thin films of TiO2, CuO and hybrid CuO/TiO2 prepared by atmospheric Chemical Vapour Deposition (Ap-CVD) and TiO2 prepared by a sol-gel process was investigated using the inactivation of bacteriophage T4 as a model for inactivation of viruses. The chemical oxidising activity was also determined by measuring stearic acid oxidation. The results showed that the rate of inactivation of bacteriophage T4 increased with increasing chemical oxidising activity with the maximum rate obtained on highly active sol-gel preparations. However these were delicate and easily damaged unlike the Ap-CVD coatings. Inactivation rates were highest on CuO and CuO/TiO2 which had the lowest chemical oxidising activities. The inactivation of T4 was higher than that of Escherichia coli on low activity surfaces. The combination of photocatalysis and toxicity of copper acted synergistically to inactivate bacteriophage T4 and retained some selfcleaning activity. The presence of phosphate ions slowed inactivation but NaCl had no effect. The results show that TiO2/CuO coated surfaces are highly antiviral and may have applications in the food and healthcare industries

Growth and formation of inverse GaP and InP opals

Opals consist of an ordered array of SiO2 spheres. This leads to a modulation of the refractive index and hence photonic stop bands behaviour over the visible/IR range of the electro-magnetic spectrum. The exact position of the stop bands depends on the size of the silica spheres. However, the refractive index contrast between the SiO2 spheres and air spaces is not great enough to open up a full photonic band gap (PBG), only the pseudogap. To increase the contrast the air spaces are filled with a material of high refractive index such as InP or GaP. To further increase the contrast the SiO2 is removed leaving a III-V framework as the inverse opal structure. By use of MOCVD we have been able to infill opals with InP and GaP to such a level that has supported the inversion of the composite forming a structure of air holes within a III-V lattice. XRD and Raman confirmed the quality of the III-V infill, while the extent of the infill was studied by SEM and reflectance measurements

1 cm2 CH3NH3PbI3 mesoporous solar cells with 17.8% steady-state efficiency by tailoring front FTO electrodes

In this article, we investigate the effects of atmospheric-pressure chemical vapour deposited fluorine doped tin oxide (FTO) thin films as front electrodes for the fabrication of mesoporous perovskite solar cells with an active area of 1 cm2 and compare them with the use of a commonly used commercial transparent conducting oxide. The effects of sheet resistance (Rs) and surface roughness are both closely linked to the film thickness. In order to separate out these effects the characteristics of the deposited FTOs were carefully controlled by changing the fluorine doping levels and the number of passes under the coating head to give films of specific thicknesses or Rs. Under AM 1.5 Sun illumination and maximum power point tracking, the optimised FTOs yielded a steady-state power conversion efficiency of 17.8%, higher than that of the reference cell fabricated from the commercial FTO. We attribute the improved cell efficiency to increased fill factor and a lower series resistance resulting from the lower Rs and increased thickness of these FTO substrates. This low-cost and viable methodology is the first such type of study looking independently at the significance of FTO roughness and resistance for highly efficient mesoporous perovskite solar cells

Growth patterns and properties of aerosol-assisted chemical vapor deposition of CH3NH3PbI3 films in a single step

In this work, we highlight growth patterns and properties of aerosol-assisted chemical vapor deposition of perovskite, CH3NH3PbI3 thin films. The substrates were distinctly covered with both perovskite and lead iodide thin films which we attribute to methylammonium iodide being the rate limiting step via mass transport. The black perovskite films demonstrated strong absorption and photoluminescence properties confirming their suitability as a light absorbing material for the fabrication of solar cells. Scanning electron microscope images showed dense morphologies along with the confirmation of holes and gaps at reduced growth temperature

Dual functionality anti-reflection and biocidal coatings

A thin film combination of anti-reflection (AR) and biocidal properties would be of particular interest to reduce the transfer of infection and improve readability of public high use touch screens. In this paper we describe the development of a dual functionality film of silica (AR) and copper oxide (biocidal). Deposition was via flame assisted chemical vapour deposition (FACVD) which has the advantages of being a cost efficient atmospheric pressure technique enabling use of non-volatile precursors and that no closed reaction cell is required so making it ideal for integration into industrial production lines. The resulting films were characterized by a range of techniques including optical spectroscopy, electron microscope and X-ray fluorescence. Biocidal behavior was tested by determining the kill rate of Escherichia coli. A 3 layer stack on glass of silica/copper oxide/silica had better adhesion and lower reflection than a comparable 2 layer stack. This multilayer film led to a > 2% drop in reflection from that of uncoated glass, similar to that of silica only film. In addition, showed a > 6 log10 kill between 6 and 24 h for as deposited and annealed samples