Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Patent
1997-05-29
1999-08-24
Goodrow, John
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
438795, H01L 310392, H01L 3118
Patent
active
059420502
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTION
The present invention relates generally to the field of solar electricity generation and in particular the invention provides an improved method of manufacturing a silicon or alloy multilayer solar cell and an improved solar cell achieved by the use of that method.
BACKGROUND OF THE INVENTION
The assignees of the present application in their earlier Australian patent application No PM4834, which is incorporated herein by reference, disclose a multilayer solar cell having significant advantages over prior art solar cells. However, fabrication of this solar cell would be challenging with conventional approaches. The present invention provides a novel manufacturing method and resulting solar cell which ameliorates some or all of the difficulties of conventional approaches while retaining the advantages of the multilayer cell structure.
SUMMARY OF THE INVENTION
A first aspect the present invention provides: multijunctional solar cell including the steps of: of layers of amorphous semiconductor material to form a multilayer structure wherein adjacent layers are characterised by differing doping levels or dopant types; layers: and temperature to thereby cause solid phase crystallization of the amorphous layers adjacent to the nucleation layer, the crystallization nucleating from the nucleation surface.
A second aspect of the present invention provides: multijunction solar cell including the steps of: of layers of amorphous semiconductor material to form a multilayer structure wherein adjacent layers are characterised by differing doping levels or dopant types; amorphous layers as a nucleation layer of crystalline or polycrystalline semiconductor material; and temperature to thereby cause solid phase crystallization of the amorphous layers adjacent to the nucleation layer, the crystallization nucleating from the nucleating layer.
A third aspect of the present invention provides: multijunction solar cell including the steps of: of layers of amorphous semiconductor material to form a multilayer structure wherein adjacent layers are characterised by differing doping levels or dopant types, amorphous layers as a nucleation layer of amorphous semiconductor material conditioned to be readily crystallized; processing the multilayer structure to cause the nucleation layer to crystallize, and temperature to thereby cause solid phase crystallization of the amorphous layers adjacent to the nucleation layer, the crystallization nucleating from the nucleation layer.
A fourth aspect of the present invention provides a semiconductor structure comprising a substrate or superstrate, a plurality of amorphous layers of semiconductor material formed on the substrate or superstrate or formed over one or more intermediate layers formed on the substrate or superstrate, and a nucleating surface formed adjacent to at least one of the amorphous layers.
In various embodiments of the invention the nucleation surface may be formed as a first surface over which the amorphous layers are formed, a last surface formed over the amorphous layers or intermediate the formation of the amorphous layers.
In preferred embodiments of the invention the semiconductor material will be silicon or an alloy of silicon and germanium. However the invention is also applicable to other semiconductor materials.
In one embodiment, the amorphous silicon nucleation layer is conditioned to be readily crystalized by way of a high doping level, typically greater than 0.1% of the solid solubility of the dopant in the crystalised material (e.g. in the range of 5.times.10.sup.17 -3.times.10.sup.21 cm .sup.-3 or higher for phosphorous in silicon) such that onset of nucleation will occur more rapidly than in other surrounding layers upon heating of the structure.
Preferably the solid phase crystallization step will cause crystallization of substantially all of the amorphous silicon layers to occur.
In one form of the invention, the nucleation layer comprises a polycrystalline layer formed directly onto the substrate or superstrate and over which the plural
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Green Martin Andrew
Shi Zhengrong
Wenham Stuart Ross
Goodrow John
Pacific Solar Pty Ltd.
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