Solar cell and method of manufacture
First Claim
1. A solar cell comprising:
- a) a silicon substrate having a front surface and a back surface,b) a plurality of first doped regions of first conductivity type in the back surface and a plurality of second doped regions of second conductivity type in the back surface, andc) a first plurality of metal contacts ohmically contacting the first doped regions at a first plurality of contact points and a second plurality of metal contacts ohmically contacting the second doped layers at a second plurality of contact points, wherein the first and second pluralities of metal contacts each comprise a thin seed layer contacting the silicon substrate and an electrically conductive layer over the seed layer which is thicker than the seed layer and wherein the seed layer comprises three layers including,a first layer that contacts the silicon and serves as an infrared reflector, the first layer comprising aluminum,a barrier layer that covers the first layer, anda layer that covers the barrier layer that serves to initiate plating.
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Accused Products
Abstract
A solar cell that is readily manufactured using processing techniques which are less expensive than microelectronic circuit processing. In preferred embodiments, printing techniques are utilized in selectively forming masks for use in etching of silicon oxide and diffusing dopants and in forming metal contacts to diffused regions. In a preferred embodiment, p-doped regions and n-doped regions are alternately formed in a surface of the wafer in offset levels through use of masking and etching techniques. Metal contacts are made to the p-regions and n-regions by first forming a seed layer stack that comprises a first layer such as aluminum that contacts silicon and functions as an infrared reflector, second layer such titanium tungsten that acts as diffusion barrier, and a third layer functions as a plating base. A thick conductive layer such as copper is then plated over the seed layer, and the seed layer between plated lines is removed. A front surface of the wafer is preferably textured by etching or mechanical abrasion with an antireflection layer provided over the textured surface. A field layer can be provided in the textured surface with the combined effect being a very low surface recombination velocity.
225 Citations
16 Claims
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1. A solar cell comprising:
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a) a silicon substrate having a front surface and a back surface, b) a plurality of first doped regions of first conductivity type in the back surface and a plurality of second doped regions of second conductivity type in the back surface, and c) a first plurality of metal contacts ohmically contacting the first doped regions at a first plurality of contact points and a second plurality of metal contacts ohmically contacting the second doped layers at a second plurality of contact points, wherein the first and second pluralities of metal contacts each comprise a thin seed layer contacting the silicon substrate and an electrically conductive layer over the seed layer which is thicker than the seed layer and wherein the seed layer comprises three layers including, a first layer that contacts the silicon and serves as an infrared reflector, the first layer comprising aluminum, a barrier layer that covers the first layer, and a layer that covers the barrier layer that serves to initiate plating. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A solar cell comprising:
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a) a silicon substrate having a front surface and a back surface, b) a plurality of first doped regions of first conductivity type in the back surface and a plurality of second doped regions of second conductivity type in the back surface, and c) a first plurality of metal contacts ohmically contacting the first doped regions at a first plurality of contact points and a second plurality of metal contacts ohmically contacting the second doped layers at a second plurality of contact points, wherein the first and second pluralities of metal contacts each comprise a thin seed layer contacting the silicon substrate and an electrically conductive layer over the seed layer which is thicker than the seed layer and wherein the seed layer is a 2-layer stack comprising; a first layer that contacts the silicon serves as an infrared reflector, the first layer comprising aluminum, and a barrier layer that covers the first layer and also serves to initiate plating.
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13. A solar cell comprising:
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a) a silicon substrate having a front surface and a back surface, b) a plurality of first doped regions of first conductivity type in the back surface and a plurality of second doped regions of second conductivity type in the back surface, c) a thermal oxide layer formed on back portions of the first doped regions and on back portions of the second doped regions, the oxide layer having a plurality of contact openings that expose selected back portions of the first and second doped regions defining a plurality of contact points, and d) a first plurality of metal contacts ohmically contacting the first doped regions through said contact openings at a first plurality of contact points and a second plurality of metal contacts ohmically contacting the second doped layers through said contact openings at a second plurality of contact points, e) the first and second pluralities of metal contacts each comprising a three layer contact surface that includes, an aluminum layer that contacts the oxide layer and contacts the exposed back portions of the first and second doped regions, wherein the interface of the aluminum layer and the oxide layer serves as an infrared reflector, a copper diffusion barrier layer that covers the aluminum layer, and a copper plating initiation layer that covers the barrier layer. - View Dependent Claims (14, 15, 16)
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Specification