Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Ralph Benhart Iverson. / M.S.

In this thesis, intrinsic hydrogenated nanocrystalline silicon thin films for solar cells application have been deposited by means of the hot &ndash / wire chemical vapour deposition (HWCVD) technique and have been characterised for their performance. It is noticed that&nbsp / hydrogenated nanocrystalline silicon is similar in some aspects (mainly optical) to its counterpart amorphous silicon actually used as the intrinsic layer in the photovoltaic industry. Substantial differences between the two materials have been found however in their respective structural and electronic properties.<br /> <br /> We show that hydrogenated nanocrystalline silicon retains good absorption coefficients known for amorphous silicon in the visible region. The order improvement and a reduced content of the bonded hydrogen in the films are linked to their good stability. We argue that provided a moderate hydrogen dilution ratio in the monosilane gas and efficient process pressure in the deposition chamber, intrinsic hydrogenated nanocrystalline silicon with photosensitivity better than 102 and most importantly resistant to the Staebler Wronski effect (SWE) can be produced. <br /> <br /> This work explores the optical, structural and electronic properties of this promising material whose study &ndash / samples have been exclusively produced in the HWCVD reactors based in the Solar Cells laboratory of the Physics department at the University of the Western Cape.

Thesis (Ph.D.)--Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Bibliography: 211-229.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 75-79). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 145-153). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 78-82). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 67-72). Also available on the World Wide Web.

M.Sc. (Physics) / Amorphous silicon is one of the most promising materials for large area solar cells for terestrial photovoltaic applications. Unfortunately these cells suffer from two serious problems: the efficiencies drop when laboratory processes are scaled up and the cells degrade after some exposure to sunlight. The exact causes of these two problems are still unknown. In this project some aspects of the latter problem were investigated. The photo-degradation was investigated by illuminating films of a-Si:H with simulated sunlight for different periods of time and then thermally annealing them. The change in the optical properties were investigated with the aid of optical transmission spectroscopy. The films were also characterized by Fourier Transform Infra-Red (FTIR) spectroscopy. The change in the electrical properties of the intrinsic films was determined as function of temperature and total photon flux. No change in the optical properties could be detected. The illumination had-no effect on the FTIR measurements. It seems as if the hydrogen is not involved in the microscopic processes leading to the Staebler-Wronski Effect (SWE). The effect of the photo-degradation manifests itself in a drop in the the dark conductivity and photoconductivity over the total temperature range that was investigated. The observed phenomena are explained in terms of photo-induced deep levels in the gap. The Fermi level shifts to the middle of the gap due to these defect states, causing a drop in the free carrier concentration and conductivity. The measurements of photoconductivity as function of photon energy show that these defect levels increase the absorption coefficient in the long wavelength region, but they also decrease the lifetime of the photo-generated carriers. The photo-induced defects were investigated with the CPM-technique. It was found that the light introduced defects deep in the band gap. The concentration of the defects increases with illumination, but saturates after about 24 hours of illumination. The defects could be annealed almost completely. The microscopic processes causing the photo-degradation of α Si:H solar cells were investigated by comparing the different theoretical models explaining the SWE with the results obtained during this project.

M.Sc. / Thin film solar cells based on polycrystalline indium diselenide (CulnSe₂) and amorphous silicon (a-Si:H) are promising candidates for the efficient conversion of sunlight into useable, cheap electrical energy. However, typical device structures are rather complex and consists of semiconductor/metal contacts as well as complicated p - n and p - i - n heterojunctions. In this study, CulnSe₂ absorber layers with excellent material properties were prepared by the selenization of metallic alloys. The a-Si:H thin films were deposited by radio frequency (RF) glow discharge in vacuum. The polycrystalline and amorphous absorber layers were deposited on glass and flexible substrates. In each case, a systematic study was conducted in which all the relevant processing parameters were varied over a broad range. These studies indicated that the structural features of the substrate significantly influence the structural features of the semiconductor thin films. The flexible substrate (kapton) was characterized by the presence of ridges, which distorted the growth behavior of the films. Deposition of ln/Cu/ln metallic alloys onto Mo coated glass (kapton) resulted in discontinuous metallic alloys, which were characterized by the presence of separated elongated island structures. The structural features of the precursors were maintained in the absorber film after selenization in elemental Se vapor. The morphological features of the CulnSe₂ absorber films were also critically influenced by the reaction temperature And reaction period to Se. The structural features on a-Si:H was significantly influenced by the structural features of the particular substrate used. Atomic force microscopy (AFM) imaging in combination with statistical analysis revealed higher roughness values when the amorphous semiconductor materials were deposited onto kapton, which negatively impacts on the device properties of solar cell devices.

No description available.