Integrated three-dimensional and planar metallization structure for thin film solar cells
A three-dimensional structure having a mixture of inverted pyramidal cavities and substantially flat areas defines the frontside and backside of a substrate. The substantially flat areas have ridges forming base openings of the inverted pyramidal cavities and planar linear regions across the substrate. Pyramidal sidewalls define the pyramidal cavities from the ridges to pyramidal apices. Metallization contacts emitter regions on the frontside of the substantially flat areas.
1. A thin film silicon substrate comprising:
a three dimensional structure defining a frontside and a backside of said substrate, said three dimensional structure comprising a mixture of a plurality of inverted pyramidal cavities and substantially flat areas;
said substantially flat areas comprising:
ridges forming base openings of said inverted pyramidal cavities; and
planar linear regions across said substrate;
said inverted pyramidal cavities comprising pyramidal sidewalls defining said pyramidal cavities from said ridges to pyramidal apices on said backside of said thin film substrate;
said thin film silicon substrate forming said ridges, linear regions, pyramidal sidewalls, and pyramidal apices having a substantially uniform layer thickness;
a first conductivity type forming doped base regions;
an emitter region having a second conductivity type on said frontside of said substantially flat areas of said thin film substrate; and
metallization on said substantially linear regions of said thin film substrate and contacting said emitter region, wherein said metallization covers at most approximately 8% of said thin film substrate frontside.
2. The substrate of claim 1 , wherein said metallization covers at most approximately 6% of said frontside of said thin film substrate.
3. The substrate of claim 1 , wherein said pyramids comprise small pyramids and large pyramids.
4. The substrate of claim 3 , wherein said small and large pyramids are offset to prevent crack formation.
5. A thin film silicon substrate comprising:
a three dimensional structure defining a frontside and a backside of said substrate, said three dimensional structure comprising a mixture of a plurality of inverted square pyramidal cavities and substantially flat areas, said plurality of inverted square pyramidal cavities comprising small square pyramids and large square pyramids arranged in an offset pattern;
said substantially flat areas comprising:
ridges forming base openings of said inverted pyramidal cavities; and
planar linear regions across said substrate;
said inverted pyramidal cavities comprising pyramidal sidewalls defining said pyramidal cavities from said ridges to pyramidal apices on said backside of said thin film silicon substrate;
said thin film silicon substrate forming said ridges, linear regions, pyramidal sidewalls, and pyramidal apices having a substantially uniform layer thickness;
a first conductivity type forming doped base regions;
an emitter region having a second conductivity type on said frontside of said substantially flat areas of said thin film substrate; and
metallization on said substantially linear regions of said thin film substrate and contacting said emitter region, wherein said metallization covers at most approximately 8% of said thin film substrate frontside.
6. The substrate of claim 5 , wherein said metallization covers at most approximately 6% of said frontside of said thin film substrate.
7. The substrate of claim 1 , wherein said substrate has a substantially uniform thickness less than 200 microns.
8. The substrate of claim 5 , wherein said substrate has a substantially uniform thickness less than 200 microns.