STRUCTURES AND METHODS FOR IMPROVING SOLAR CELL EFFICIENCY AND MECHANICAL STRENGTH
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.
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.