Structures and methods for improving solar cell efficiency and mechanical strength

Abstract

The present disclosure presents a three-dimensional thin film solar cell (3-D TFSC) substrate having enhanced mechanical strength, light trapping, and metal modulation coverage properties. The substrate includes a plurality of unit cells, which may or may not be different. Unit cells are defined as a small self-contained geometrical pattern which may be repeated. Each unit cell structure includes a wall enclosing a trench. Further, the unit cell includes an aperture having an aperture diameter. For the purposes of the present disclosure, the dimensions of interest include wall thickness, wall height, and aperture diameter. A pre-determined variation in these dimensions among unit cells across the substrate produces specific advantages.

What is claimed is: 
     
         1 . A three-dimensional thin film solar cell substrate comprising:
 a plurality of unit cells, wherein each said unit cell comprises:
 a wall enclosing a trench, said wall having a wall thickness and a wall height; and 
 an aperture having an aperture diameter; and 
   a predetermined variation in at least one of said wall thickness, said wall height, and said aperture diameter among said plurality of unit cells.   
     
     
         2 . The substrate of  claim 1 , wherein said predetermined variation further comprises a predetermined variation in at least two of said wall thickness, said wall height, and said aperture diameter among said plurality of unit cells. 
     
     
         3 . The substrate of  claim 1 , wherein said predetermined variation further comprises at least one of a local variation, a global variation, a periodic variation, a non-periodic variation, a gradual variation, or an abrupt variation. 
     
     
         4 . The substrate of  claim 1 , wherein said predetermined variation further comprises a reduction in said aperture diameter towards at least one edge of said three-dimensional thin film solar cell substrate. 
     
     
         5 . The substrate of  claim 1 , wherein said predetermined variation further comprises a grid-like pattern of a first group of unit cells comprising a larger aperture diameter and a second group of unit cells comprising a smaller aperture diameter. 
     
     
         6 . The substrate of  claim 1 , wherein said predetermined variation further comprises at least three different aperture diameters. 
     
     
         7 . The substrate of  claim 1 , wherein said predetermined variation further comprises a reduction in said wall thickness towards at least one edge of said three-dimensional thin film solar cell substrate. 
     
     
         8 . The substrate of  claim 1 , wherein said unit cell further comprises at least one light scattering feature inside of said trench. 
     
     
         9 . A mask for forming a three-dimensional thin film solar cell substrate, said mask comprising:
 a plurality of unit cells, wherein each of said unit cells comprises:
 a wall enclosing a trench, said wall having a wall thickness and a wall height; and 
 an aperture having an aperture diameter; and 
   a predetermined variation in at least one of said wall thickness, said wall height, and said aperture diameter among said plurality of unit cells.   
     
     
         10 . The mask of  claim 9 , wherein said predetermined variation further comprises a predetermined variation in at least two of said wall thickness, said wall height, and said aperture diameter among said plurality of unit cells. 
     
     
         11 . The mask of  claim 9 , wherein said predetermined variation further comprises at least one of a local variation, a global variation, a periodic variation, a non-periodic variation, a gradual variation, or an abrupt variation. 
     
     
         12 . The mask of  claim 9 , wherein said predetermined variation further comprises a reduction in said aperture diameter towards at least one edge of said mask. 
     
     
         13 . The mask of  claim 9 , wherein said predetermined variation further comprises a grid-like pattern of a first group of unit cells comprising a larger aperture diameter and a second group of unit cells comprising a smaller aperture diameter. 
     
     
         14 . The mask of  claim 9 , wherein said predetermined variation further comprises at least three different aperture diameters. 
     
     
         15 . The mask of  claim 9 , wherein said predetermined variation further comprises a reduction or increase in said wall thickness towards at least one edge of said mask. 
     
     
         16 . The mask of  claim 9 , wherein said unit cell further comprises at least one light scattering feature inside of said trench. 
     
     
         17 . A method for manufacturing a three-dimensional thin film solar cell substrate, comprising the steps of:
 forming a template having a plurality of unit cell formation areas, wherein each of said unit cell formation areas comprises:
 a wall formation area enclosing a trench formation area, said wall formation area having a wall thickness and a wall height; and 
 an aperture formation area having an aperture diameter; 
   varying at least one of said wall thickness, said wall height, and said aperture diameter among said plurality of unit cell formation areas;   forming a release layer on said template;   forming a three-dimensional thin film solar cell substrate on said release layer; and   releasing said three-dimensional thin film solar cell substrate.   
     
     
         18 . The method of  claim 17 , wherein said step of varying further comprises the step of varying said aperture diameter. 
     
     
         19 . The method of  claim 17 , wherein said step of varying further comprises the step of varying said aperture diameter in a grid-like pattern. 
     
     
         20 . The method of  claim 17 , wherein said step of varying further comprises the step of varying said wall thickness.