41 research outputs found
Properties of Al-doped ZnS films grown by chemical bath deposition
No full textZinc sulphide (ZnS) buffer layers are a cadmium free, wider energy band gap, alternative to the cadmium sulphide(CdS) buffer layers commonly used in copper indium gallium diselenide (CuInGaSe2)-based solar cells. However extrinsic doping of the ZnS is important to lower the resistivity of the layers and to improve flexibility of device design. In this work, Al-doped ZnS nanocrystalline films have been produced on glass substrates using a chemical bath deposition (CBD) method. The Al- concentration was varied from 0 at. % to 10 at. %, keeping other deposition parameters constant. The elemental composition of a typical sample with 6 at. % ‘Al’ in ZnS was Zn=44.9 at. %, S=49.8 at. % and Al=5.3 at.%. The X-ray diffraction data taken on these samples showed a broad peak corresponding to the (111) plane of ZnS while the crystallite size varied in the range, 8 – 15 nm, depending on the concentration of Al in the layers. The films with a Al-doping content of 6 at. % had an optical transmittance of 75 % in the visible range and the energy band gap evaluated from the data was 3.66 eV. The films n-type electrical conductivities and the electrical resistivity varied in the range, 107-103 Ωcm, it decreasing with an increase of the Al-concentration in the solution
Nano-Photonic Structures for Light Trapping in Ultra-Thin Crystalline Silicon Solar Cells
Get PDFThick wafer-silicon is the dominant solar cell technology. It is of great interest to develop ultra-thin solar cells that can reduce materials usage, but still achieve acceptable performance and high solar absorption. Accordingly, we developed a highly absorbing ultra-thin crystalline Si based solar cell architecture using periodically patterned front and rear dielectric nanocone arrays which provide enhanced light trapping. The rear nanocones are embedded in a silver back reflector. In contrast to previous approaches, we utilize dielectric photonic crystals with a completely flat silicon absorber layer, providing expected high electronic quality and low carrier recombination. This architecture creates a dense mesh of wave-guided modes at near-infrared wavelengths in the absorber layer, generating enhanced absorption. For thin silicon (<2 μm) and 750 nm pitch arrays, scattering matrix simulations predict enhancements exceeding 90%. Absorption approaches the Lambertian limit at small thicknesses (<10 μm) and is slightly lower (by ~5%) at wafer-scale thicknesses. Parasitic losses are ~25% for ultra-thin (2 μm) silicon and just 1%–2% for thicker (>100 μm) cells. There is potential for 20 μm thick cells to provide 30 mA/cm2 photo-current and >20% efficiency. This architecture has great promise for ultra-thin silicon solar panels with reduced material utilization and enhanced light-trapping
Somdet Phrachaoborommawongthoe Kromphraya Sudarattanaratchaprayun prathap bon tang
No full textThe author presents an old photograph of Somdet Phrachaoborommawongthoe Kromphraya Sudarattanaratchaprayun, a daughter of King Rama III. This picture was taken by King Rama V in 1868. The author uses this picture as an evidence to claim that another picture of the same women which is almost identical to this one was also taken by King Rama V at about the same time
Thin Films of Tin Sulphide for Application in Photovoltaic Solar Cells
No full textTin sulphide (SnS) is a promising new material for use in photovoltaic solar cells. With a direct energy band gap of about 1.3 eV, and a high optical absorption coefficient, only a few microns of SnS are needed to absorb most of the incident light. Not only is SnS made of abundant, environmentally acceptable elements, it is also amphoteric giving flexibility to device design. Structures that can be envisioned include p-type SnS (absorber layer) / n-type (window layer) heterojunction devices, buried p-n junction devices made using SnS and p-i-n structure devices where the i-layer is SnS. It is most likely that the grain boundaries in SnS can be passivated either by counter-doping the grain boundaries, or by oxidizing the grain boundaries to form wide energy bandgap n-type SnO2 within p-type SnS, as dopants or oxygen will diffuse preferentially down the grain boundaries and react first at the grain boundary surfaces. Thin film solar cell devices based on the use of SnS have now been produced with efficiencies > 2 %; these and other promising results indicate that it is most likely that devices with efficiencies > 10% will be produced in the near future. Given that tin layers are routinely coated in industry over large area substrates and that industrial sulphidization processes are also well established, the industrialization of this technology should be more straightforward than that encountered with the already commercialised cadmium telluride and copper indium gallium diselenide thin film technologies. This review discusses the chemical and physical properties of SnS, the methods of producing both bulk crystals and thin films of SnS, the literature available on studies of SnS2 based photovoltaic solar cell devices, and progress made so far in developing this exciting new material
Aluminum-Induced crystallization: Applications in photovoltaic technologies
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Role of bicarbonate as a pH buffer and electron sink in microbial dechlorination of chloroethenes
Get PDFAbstract Background Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3−) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3− also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2). We studied the effect of HCO3− as a buffering agent and the effect of HCO3−-consuming reactions in a range of concentrations (2.5-30 mM) with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens. Results Rate differences in TCE dechlorination were observed as a result of added varying HCO3− concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7) from biological HCO3− consumption. Significantly faster dechlorination rates were noted at all HCO3− concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3− concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3− were provided initially. Conclusions Our study reveals that HCO3− is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3− and the changes in pH exerted by methanogens and homoacetogens.</p
Somdet Phrachaoborommawongthoe Kromphraya Sudarattanaratchaprayun prathap bon phra kao-ai
No full textThe author presents an old photograph which he speculates that it was taken by King Rama V in 1868. The author took a copy of the picture from the book regarding the evolvement of Thai customs during the early Rattanakosin period. The photograph portrays Somdet Phrachaoborommawongthoe Kromphraya Sudarattanaratchaprayun, a daughter of King Rama III, was sitting on a modern style chair. In addition to describing a style of dress wore by this royal woman, the author also briefly describes her biography
