Composition control for roll-to-roll processed photovoltaic films

Abstract

The present invention provides methods of electroplating a film or films onto a top surface of a continuously moving roll-to-roll sheet. In one aspect, the invention includes continuously electroplating a film onto a conductive surface using an electroplating unit as the roll-to-roll sheet moves therethrough, detecting a thickness of the film electroplated onto a portion of the roll-to-roll sheet and generating a thickness signal corresponding thereto. In this aspect, when continuously electroplating, the thickness of the film is adjusted toward a predetermined thickness value using the thickness signal for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein:

FIG. 1 is a cross-sectional view of a solar cell employing a Group IBIIIAVIA absorber layer.

FIG. 2 is a schematic of a roll-to-roll electroplating system to deposit a precursor layer that may be used for the formation of a Group IBIIIAVIA absorber layer.

FIG. 3A is a flexible foil base.

FIG. 3B is a flexible foil base with an electroplated Cu/Ga/In precursor stack.

FIG. 4 shows a side view of a roll-to-roll electrodeposition system comprising a Cu-processing-unit, a Ga-processing-unit, and an In-processing-unit with their associated metrology-stations.

FIG. 5 shows a top view of a Cu-processing-unit and a Cu-metrology-station.

Claims

1. A method of electroplating a film onto a conductive surface of a continuously moving roll-to-roll sheet comprising the steps of: continuously moving the roll-to-roll sheet through an electroplating unit so that continuous portions of the conductive surface are positioned for electroplating to occur thereon when disposed in the electroplating unit;continuously electroplating the film onto the conductive surface using the electroplating unit as the roll-to-roll sheet moves therethrough; anddetecting a thickness of the film electroplated onto a portion of the roll-to-roll sheet and generating a thickness signal corresponding thereto;wherein the step of continuously electroplating includes the step of adjusting the thickness of the film toward a predetermined thickness value using the thickness signal for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet.

2. The method according to claim 1 wherein the step of detecting is performed using X-ray fluorescence.

3. The method according to claim 2 wherein the steps of detecting and adjusting are repeated so that the thickness of the film is kept substantially at the predetermined thickness value on substantially the whole of the roll-to-roll sheet.

4. The method according to claim 3 wherein the film includes one of Cu, In and Ga.

5. The method according to claim 4 wherein the step of adjusting alters a deposition current density used by the electroplating unit based upon the thickness signal, thereby adjusting the thickness of the subsequent portion of the film.

6. The method according to claim 4 wherein the step of adjusting alters an effective electroplating length used by the electroplating unit based upon the thickness signal, thereby adjusting the thickness of the subsequent portion of the film.

7. The method according to claim 4 wherein the conductive surface comprises at least one of Ru, Ir, Os, Cu, In and Ga.

8. The method according to claim 7 wherein the film comprises Cu and the conductive surface comprises one of Ru, Ir, Os, In and Ga.

9. The method according to claim 7 wherein the film comprises Ga and the conductive surface comprises one of Cu and In.

10. The method according to claim 7 wherein the film comprises In and the conductive surface comprises one of Cu and Ga.

11. The method according to claim 1 wherein the step of detecting detects the thickness of the film at a plurality of locations across a width of the continuously moving roll-to-roll sheet to obtain a corresponding plurality of thickness signals; wherein the step of adjusting adjusts the thickness of the film toward the predetermined thickness value using the plurality of thickness signals for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet, such that the thickness is adjusted taking into consideration the location of the detecting.

12. The method according to claim 11 wherein the corresponding plurality of thickness signals each control a current density of a corresponding plurality of anodes for the step of adjusting.

13. The method according to claim 11 wherein the corresponding plurality of thickness signals each control an effective electroplating length of a corresponding plurality of anodes for the step of adjusting.

14. The method according to claim 11 wherein the step of detecting is performed using X-ray fluorescence.

15. The method according to claim 1 wherein the thickness signal indicates at least one of a normal value, low value, or high value, wherein the high value causes electroplating a lower thickness for the subsequent portion, and wherein the low value causes electroplating a greater thickness for the subsequent portion.

16. The method according to claim 15 wherein the step of detecting is performed using X-ray fluorescence.

17. The method according to claim 1 further including the step of continuously electroplating another film at another deposition current density onto the film using another electroplating unit disposed adjacent to the electroplating unit as the roll-to-roll sheet moves through the another electroplating unit.

18. A method of electroplating a stacked layer of a plurality of films in a plurality of sequentially disposed electroplating units onto a continuously moving roll-to-roll sheet comprising the steps of: continuously moving the roll-to-roll sheet through each of the plurality of sequentially disposed electroplating units so that continuous portions of a top surface of the roll-to-roll sheet are positioned for electroplating to occur thereover when disposed in each of the electroplating units;continuously electroplating each one of the films over the top surface of the roll-to-roll sheet using each of the electroplating units as the roll-to-roll sheet moves therethrough; anddetecting a thickness of each of the films electroplated over a portion of the roll-to-roll sheet and generating a thickness signal corresponding thereto;wherein the step of continuously electroplating includes the step of adjusting the thickness of each of the films toward a predetermined thickness value for that film using the thickness signal for that film for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet.

19. The method according to claim 18 wherein the plurality of sequentially disposed electroplating units comprise at least one Cu electroplating unit, at least one Ga electroplating unit and at least one In electroplating unit.

20. The method according to claim 18 wherein the step of detecting is performed using X-ray fluorescence.

21. The method according to claim 18 wherein the step of adjusting alters a deposition current density used by the electroplating unit based upon the thickness signal, thereby adjusting the thickness of the subsequent portion of the film.

22. The method according to claim 18 wherein the step of adjusting alters an effective electroplating length used by the electroplating unit based upon the thickness signal, thereby adjusting the thickness of the subsequent portion of the film.

23. The method according to claim 18 wherein the step of detecting detects the thickness of the film at a plurality of locations across a width of the continuously moving roll-to-roll sheet to obtain a corresponding plurality of thickness signals; wherein the step of adjusting adjusts the thickness of the film toward the predetermined thickness value using the plurality of thickness signals for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet, such that the thickness is adjusted taking into consideration the location of the detecting.

24. The method according to claim 23 wherein the corresponding plurality of thickness signals each control a current density of a corresponding plurality of anodes for the step of adjusting.

25. The method according to claim 23 wherein the corresponding plurality of thickness signals each control an effective electroplating length of a corresponding plurality of anodes for the step of adjusting.

26. The method according to claim 23 wherein the step of detecting is performed using X-ray fluorescence.

27. A method of controlling electroplating of a plurality of different films in a plurality of sequentially disposed electroplating units onto a top surface of a continuously moving roll-to-roll sheet comprising the steps of: continuously moving the roll-to-roll sheet through each of the plurality of electroplating units so that continuous portions of the top surface are positioned for electroplating to occur thereon when disposed in the electroplating units;continuously electroplating a first film onto the top surface of the continuously moving roll-to-roll sheet;detecting a thickness of the first film and generating a thickness signal corresponding thereto;continuously electroplating a second film over the first film, wherein a thickness of the electroplated second film is controlled by the thickness signal.

28. The method according to claim 27 wherein the control by the thickness signal results in a substantially same molar ratio of a first material used in the first film to a second material used in the second film at substantially each location along the moving substrate.

29. The method according to 28 wherein, the first material and the second material each include at least one of Cu, In and Ga.

30. The method according to 29 wherein the top surface comprises at least one of Ru, Os and Ir.

31. The method according to claim 30 wherein the step of detecting is performed using X-ray fluorescence.

32. The method according to claim 27 wherein the step of detecting is performed using X-ray fluorescence.

33. The method according to claim 27 wherein the first film is comprised of at least a first sub-film and second sub-film, each of the first and second sub-films being separately electroplated; wherein the step of detecting detects the thickness of both sub-films at the same time, thereby resulting in a first sub-film thickness signal and a second sub-film thickness signal; andwherein the first sub-film thickness signal and the second sub-film thickness signal are both used to generate the thickness signal used in the step of continuously electroplating the second film.

34. The method according to claim 33 wherein the step of detecting is performed using X-ray fluorescence.

35. The method according to claim 33 wherein the first sub-film is Cu and the second sub-film is Ga.

36. The method according to claim 35 further including the step of heat treating the first film prior to the step of detecting.

47. The method according to claim 27 further including the step of electroplating a third material over the second film.

48. The method according to claim 27 further including the steps of: continuously electroplating a third film onto the second film using an electroplating unit as the roll-to-roll sheet moves therethrough; anddetecting a thickness of the third film electroplated onto a portion of the second film and generating another thickness signal corresponding thereto;wherein the step of continuously electroplating the third film includes the step of adjusting the thickness of the third film toward a predetermined thickness value using the another thickness signal for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet.

49. The method according to claim 48 wherein both steps of detecting are performed using X-ray fluorescence.

50. The method according to claim 27 wherein the step of detecting detects the thickness of the first film at a plurality of locations across a width of the continuously moving roll-to-roll sheet to obtain a corresponding plurality of thickness signals; wherein the step of adjusting adjusts the thickness of the second film using the plurality of thickness signals for a subsequent portion of the roll-to-roll sheet that follows the portion of the roll-to-roll sheet, such that the thickness is adjusted taking into consideration the location of the detecting.

51. A method of controlling electroplating of a plurality of films onto a continuously moving roll-to-roll sheet using a plurality of sequentially disposed electroplating units comprising the steps of: continuously moving the roll-to-roll sheet through each of the plurality of sequentially disposed electroplating units so that continuous portions of a top surface of the roll-to-roll sheet are positioned for electroplating to occur thereon when disposed in each of the electroplating units;continuously electroplating a first film on a top surface of continuously moving roll-to-roll sheet;detecting the thickness of the electroplated first film at a plurality of locations across a width of the continuously moving roll-to-roll sheet to obtain a corresponding plurality of thickness signals;continuously electroplating a second film over the first film;wherein the plurality of thickness signals are used to adjust a thickness of at least one of the first film and the second film, such that the thickness is adjusted taking into consideration the location of the detecting.

52. The method according to claim 51 wherein the step of detecting includes the step of applying an algorithm to determine how much to adjust the thickness at each location across the width of the substrate.

53. The method according to claim 51 wherein the step of detecting is performed using X-ray fluorescence.