| 摘要 |
1514548 Photovoltaic devices SONY CORP 17 Oct 1975 [19 Oct 1974] 42806/75 Heading H1K A photovoltaic semiconductor device comprises a series of 2N zones (where N is an integer > 1) alternately of P and N type, all zones, apart from the two outermost from which the output is derived, having a thickness less than the minority carrier diffusion length therein whereby transistor action can take place across them. For optimum output the construction should be such that the transistors of which the two outermost zones are the emitters have normal current amplification factors a above 0À65 and preferably substantially 1, and the inverse as of these transistors and the normal and inverse as of transistors formed by groups of inner zones are between 0À2 and 0À7, preferably 0À5. In one device, Fig. 4, based on an N type Si substrate 3 the inner P zone 4 is formed by epitaxy or diffusion and the outer zones 2, 5 by diffusion, and the light receiving face, which has a reflection reducing coating 9, e.g. of polysilicon containing oxygen and optionally nitrogen, carries a comb-shaped electrode 6. A first alternative structure with its junctions nearer the light receiving face to improve its short wavelength response is formed on a relatively thick N substrate forming one end zone. The emitter efficiency of each end zone is improved by highly doping its surface to provide an LH junction within a diffusion length of the emitter junction. In a modification of this for use in the inverted position to provide an enhanced long wavelength response the high surface doping of the N zone is confined to the area beneath the electrode to reduce unwanted absorption. Details of doping levels, dimensions and processing steps are given.
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