FINE GEOMETRY SOLAR CELL

摘要

1395200 Solar cells COMMUNICATIONS SATELLITE CORP 27 Sept 1972 [28 Sept 1971] 44564/72 Heading H1K A solar cell comprises a 500-2000Š thick layer of one conductivity type forming a PN junction with an underlying semi-conductor substrate. An electrode formed by photolithographic steps comprises a large number of metal strips each between 1 and 20 Á wide and occupies at most 10% of the layer area A typical cell is made by diffusing phosphorus, arsenic or antimony into one face of a P type silicon wafer to a depth of 1500Š by specified methods to give a surface impurity concentration of 1019-1020 atoms/cc. The damaged top 500Š of the diffused layer is then oxidized by heating in steam and the oxide preferably removed. An electrode consisting of fine strips perpendicular to a connecting busbar or strips parallel to the busbar and connected to it by tapered intermediate bus-bars is then provided. In one example the electrode pattern is first defined by exposing a photoresist coating to light or an electron beam and developing. A 300Š layer of chromium and a superposed 2000Š layer of silver are then deposited overall and the undeveloped photoresist dissolved to remove the overlying metal. The remaining electrode metal is then thickened tp 20. Á. by plating with silver. Alternatively the chromium is overcoated with a 20 Á layer of gold which is then silver plated, or chromium deposited over the entire N type layer and form etched with the aid of a photoresist mask. Gallium arsenide is an alternative semiconductor material.