AMORPHOUS SILICON PHOTOVOLTAIC JUNCTIONS PRODUCED BY GAS PHASE DOPING AND BY ION IMPLANTATION
The two main aims of the joint Dundee-Heidelberg project were to explore the design and properties of a-Si photovoltaic junctions and to investigate electronic and structural properties of the material relevant to its photovoltaic applications. A-Si solar cells have been produced using both gas phase and implantation doping. It is shown that both techniques lead to devices with conversion efficiencies between 5 and 6% and it is suggested that ion implantation is the solution to the 3-chamber process of deposition now used in mass production. Fast transient techniques have been developed for direct application to photovoltaic cells to provide information on carrier mobilities, lifetimes and the built-in field. One of the most important conclusions has been that the observed "lifetime limitations" are determined by the non- uniformity of the internal field of the junctions and not by the electronic properties of the material. The controversial problem of photogeneration has been investigated. It is shown that in a-Si germinated recombination plays a negligible part at photon energies above the band gap and that the quantum efficiency for photogeneration lies between 0.9 and 1.0. Depth profiles of H and other elements have been measured using nuclear techniques in order to control the actual impurity distribution introduced by gas phase and ion implantation processes. The important question of atomic diffusion in disordered systems has been systematically investigated using the a-Si system and representation members of most important impurity groups. So far, the general conclusion is that diffusion in a-Si is impeded rather than enhanced over the crystalline matrix.
Bibliographic Reference: EUR 9958 EN (1985) MF, 38 P., BFR 150, BLOW-UP COPY BFR 200, EUROFFICE, LUXEMBOURG, POB 1003
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Record Number: 1989124104800 / Last updated on: 1987-01-01
Available languages: en