Barbara Swatowska

Graphene platelets as morphology tailoring additive in carbon nanotube transparent and flexible electrodes for heating applications

Flexible and transparent electrodes were fabricated with spray coating technique from paints based on multiwalled carbon nanotubes with the addition of graphene platelets. The work presents the influence of graphene platelets on the paints rheology and layers morphology, which has a strong connection to the electrooptical parameters of the electrodes. The paints rheology affects the atomization during spray coating and later the leveling of the coating on the substrate. Both technological aspects shape the morphology of the electrode and the distribution of nanoparticles in the coating. All these factors influence the sheet resistance and roughness, which is linked to the optical transmission and absorbance. In our research the electrode was applied as a transparent and elastic heating element with 68% optical transmission at 550 nm wavelength and 8.4 kΩ/• sheet resistance. The elastic heating element was tested with a thermal camera at the 3 diverse supply voltages -20, 30, and 60 VDC. The test successfully confirmed and supported our proposed uses of elaborated electrodes.

Structural and Optical Properties of Spray Coated Carbon Hybrid Materials Applied to Transparent and Flexible Electrodes

Transparent and flexible electrodes were fabricated with cost-effective spray coating technique on polyethylene terephthalate foil substrates. Particularly designed paint compositions contained mixtures of multiwalled carbon nanotubes and graphene platelets to achieve their desired rheology and electrooptical layers parameters. Electrodes were prepared in standard technological conditions without the need of clean rooms or high temperature processing. The sheet resistance and optical transmittance of fabricated layers were tuned with the number of coatings; then the most suitable relation of these parameters was designated through the figure of merit. Optical measurements were performed in the range of wavelengths from 250 to 2500 nm with a spectrophotometer with the integration sphere. Spectral dependence of total and diffusive optical transmission for thin films with graphene platelet covered by multiwalled carbon nanotubes was designated which allowed determining the relative absorbance. Layer parameters such as thickness, refractive index, energy gap, and effective reflectance coefficient show the correlation of electrooptical properties with the technological conditions. Moreover the structural properties of fabricated layers were examined by means of the X-ray diffraction.

Carbon nanomaterials dedicated to heating systems

Purpose – The paper aims to present the research results related to transparent heating elements made from carbon nanomaterials. Heating elements were fabricated only with cost-effective techniques with the aim to be easily implemented in large area applications. Presented materials and methods are an interesting alternative to vacuum deposition of transparent resistive layers and etching of low-resistive patterns. Fabricated heating elements were designed to be used as de-icing structures in roof-top windows. Design/methodology/approach – The paper presents the research results related to transparent heating elements made from carbon nanomaterials. Heating elements were fabricated only with cost-effective techniques with the aim to be easily implemented in large area applications. Presented materials and methods are an interesting alternative to vacuum deposition of transparent resistive layers and etching of low-resistive patterns. Fabricated heating elements were designed to be used as de-icing structu...

Boron liquid solution deposited by spray method for p-type emitter formation in crystalline Si solar cells

This paper reports the fabrication of n-type crystalline Si based solar cell using boron liquid solution (BLS) deposited by spray method for p-type emitter formation. The X-ray photoelectron spectroscopy (XPS) was used for the analysis of surface composition and electronic states of elements at the glass layer of dopant (GLD) obtained from BLS. The investigation of the borosilicate glass layer (BSG) created on a base of GLD during diffusion process were carried out by transmission electron microscopy (TEM). The diffusion profiles were determined by secondary ion mass spectrometry (SIMS) and electrochemical capacitance-voltage (EC-V) techniques, whereas the solar cells were characterized by the light current-voltage (I-V) and spectral measurements. The influence of a doping process on a minority carrier lifetime of the Si wafers was detected by quasi-steady-state photoconductance technique. Application of the elaborated BSL allowed to obtain the p-type Si emitters from BSG layer which exhibits unproblematic etching behaviour after diffusion process and final fabrication of the solar cells with the fill factor of 74% and photoconversion efficiency of 13.04 %. The elaborated BLS is a source which offers an attractive practicable alternative to form emitters on the n-type Si substrate.

a-SiCxNy:H thin films for applications in solar cells as passivation and antireflective coatings

Amorphous a-SiCxNy:H thin films may be an alternative to a-Si:N:H coatings which are commonly used in silicon solar cells. This material was obtained by PECVD (13.56 MHz) method. The reaction gases used: silane, methane, nitrogen and ammonia. The structure of the layers were investigated by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). IR absorption spectra of a-SiCxNy:H layers confirmed the presence of various hydrogen bonds – it is important for passivation of Si structural defects. The ellipsometric measurements were implemented to determine the thickness of layers d, refractive index n, extinction coefficient k and energy gap Eg. The values of the energy gap of a-SiCxNy:H layers are in the range from 1.89 to 4.34 eV. The correlation between energy gap of materials and refractive index was found. Generally the introduction of N and/or C into the amorphous silicon network rapidly increases the Eg values.

Characterisation and application of WO3 films for electrochromic devices

Electrochromic system is the one of the most popular devices using color memory effect under the influence of an applied voltage. The electrochromic system was produced based on the thin WO3 electrochromic films. Films were prepared by RF magnetron sputtering from tungsten targets in a reactive Ar+O2 gas atmosphere of various Ar/O2 ratios. The technological gas mixture pressure was 3 Pa and process temperature 30°C. Structural and optical properties of WO3 films were investigated for as-deposited and heat treated samples at temperature range from 350°C to 450°C in air. The material revealed the dependence of properties on preparation conditions and on post-deposition heat treatment. Main parameters of thin WO3 films: thickness d, refractive index n, extinction coefficient k and energy gap Eg were determined and optimized for application in electrochromic system. The main components of the system were glass plate with transparent conducting oxides, electrolyte, and glass plate with transparent conducting oxides and WO3 layer. The optical properties of the system were investigated when a voltage was applied across it. The electrochromic cell revealed the controllable transmittance depended on the operation voltage.

Modified structures of multicrystalline silicon as light detectors

Photovoltaic structures of multicrystalline silicon were modified by the deposition of a-Si:C:H thin films. The films have been deposited by Plasma Enhanced Chemical Vapor Deposition at 13.56 MHz in SiH4 +CH4 gaseous mixtures. The structures have been investigated by means of optical and electrical methods. Spectral photosensitivity measurements were done at room temperature in voltage and current modes. The signal was registered in the function of light in the visible and near infrared region from 400 to 1100 nm. Silicon structures covered by a-Si:C:H have higher spectral photosensitivities than uncover ones and the apparent increase in efficiency has been observed.