| 摘要 |
A cell for converting received light energy to electrical energy comprises, in the simplest embodiment, four layers of differing types of semiconductive material stacked so as to form three opposite conductivity junctions. The outer two, "active", junctions are formed of confronting layers with matched lattice constants so as to provide a plurality of energy converters. The center, "connective", junction is formed by two confronting intermediate layers which have purposely mismatched lattice constants so as to provide a lattice defect site surrounding the center junction. Majority carriers (electrons and holes) will recombine at the lattice defects. This will cause the connective junction, although of apparently reverse-biased opposite conductivity type layers, to act as a low resistance ohmic connection or substantial short circuit so as to connect the energy converting portions in series. Due to the stacked arrangement of junctions in which the layers forming the active junctions have increasingly lower bandgaps toward the bottom of the stack, incident photons are converted to electrical energy with far greater efficiency than in a single-junction arrangement. Preferably the stacked layers are formed of suitably-doped epitaxially-grown layers of compounds of III-V elements (Ga, In, Al, As, P, Sb). The number of active junctions is preferably made greater than two, e.g., six is currently regarded as a practical maximum. Low resistance interconnections between the energy converting portions formed by active junctions are provided by connective junctions which are formed of lattice constant mismatched and opposite conductivity confronting layers.
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