Method for making optically enhanced thin film photovoltaic device using lithography defined random surfaces

Claim 1

A method for producing an optically enhanced thin film photovoltaic semiconductor device having electrical contacts to carry current from said device comprising: a. producing an active layer of semiconductor material wherein the surface of at least one side of said active layer is textured such that said surface includes randomly spaced, densely packed microstructures of predetermined dimensions of the order of the wavelength of visible light in said semiconductor material, said microstructure being microcolumnar posts having a predetermined profile such that said texture of said active layer results in optically enhancement by incoherent scattering with a randomization fraction, β, greater than 0.75; b. forming a reflecting surface directly to either side of said semiconductor material and making an ohmic contact to said material such that the parasitic optical absorption in said electrical contacts and said reflecting surface are less than 1/n 2 , where n is the semiconductor index of refraction, such that the enhancement factor, E, for optical absorption within the active layer of the semiconductor material and the quantum efficiency of collection of photogenerated carriers in increased by a factor greater than 1.5 n 2 .

Claim 2

A method for producing an optically enhanced thin film photovoltaic semiconductor device having electrical contacts to carry current from said device comprising: a. producing an active layer of semiconductor material wherein the surface of at least one side of said active layer is textured such that said surface includes randomly spaced, densely packed microstructures of predetermined dimensions of the order of the wavelength of visible light in said semiconductor material, said microstructure being microcolumnar posts having a predetermined profile such that said texture of said active layer results in optically enhancement by incoherent scattering with a randomization fraction, β, greater than 0.75; b. forming a reflecting surface directly to either side of said semiconductor material and making an ohmic contact to said material such that the parasitic optical absorption in said electrical contacts and said reflecting surface are less than 1/n 2 , where n is the semiconductor index of refraction, such that the enhancement factor, E, for optical absorption within the active layer of the semiconductor material and the quantum efficiency of collection of photogenerated carriers in increased by a factor greater than 1.5 n 2 .

Claim 12

A method for producing an optically enhanced thin film photovoltaic semiconductor device comprising: a. producing a textured surface on a substrate, wherein said textured surface includes randomly spaced, densely packed microstructures of predetermined dimensions of the order of the wavelength of visible light in the semiconductor material of said device, said microstructures being microcolumnar posts having a predetermined profile, such that said texture of said active layer results in optical enhancement by incoherent scattering; b. forming a reflecting surface on said substrate, said reflecting surface conforming to the shape of said textured substrate such that the parasitic optical absorption in said diffusion barrier is less than 5/n 2 , where n is the semiconductor index of refraction c. forming a conducting transparent diffusion barrier to said reflecting surface, said diffusion barrier conforming to the shape of said reflecting surface; d. depositing semiconductor material on said diffusion barrier forming an ohmic contact, such that the parasitic optical absorption in said contact is less than 5/n 2 , where n is the semiconductor index of refraction, said semiconductor material conforming to the shape of said diffusion barrier, and; e. attaching a transparent ohmic contact to said semiconductor material on the side away from said substrate such that the parasitic optical absorption in said diffusion barrier is less than 5/n 2 , where n is the semiconductor index of refraction.

Claim 13

A method for producing an optically enhanced thin film photovoltaic semiconductor device comprising: a. producing a textured surface on a substrate, wherein said textured surface includes randomly spaced, densely packed microstructures of predetermined dimensions of the order of the wavelength of visible light in the semiconductor material of said device, said microstructures being microcolumnar posts having a predetermined profile, such that said texture of said active layer results in optical enhancement by incoherent scattering; b. forming a reflecting surface on said substrate, said reflecting surface conforming to the shape of said textured substrate such that the parasitic optical absorption in said diffusion barrier is less than 5/n 2 , where n is the semiconductor index of refraction c. forming a conducting transparent diffusion barrier to said reflecting surface, said diffusion barrier conforming to the shape of said reflecting surface; d. depositing semiconductor material on said diffusion barrier forming an ohmic contact, such that the parasitic optical absorption in said contact is less than 5/n 2 , where n is the semiconductor index of refraction, said semiconductor material conforming to the shape of said diffusion barrier, and; e. attaching a transparent ohmic contact to said semiconductor material on the side away from said substrate such that the parasitic optical absorption in said diffusion barrier is less than 5/n 2 , where n is the semiconductor index of refraction.