SOLAR CELL COMPRISING NEIGHBORING ELECTRICALLY INSULATING PASSIVATION REGIONS HAVING HIGH SURFACE CHARGES OF OPPOSING POLARITIES AND PRODUCTION METHOD

• US 20120073647A1
• Filed: 06/01/2010
• Published: 03/29/2012
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: Helmholtz-Zentrum Berlin FüR Materialien und Energie Gesellschaft Mit Beschrã¤Nkter Haftung (Bundesrepublik Deutschland)
• Original Assignee: Helmholtz-Zentrum Berlin FüR Materialien und Energie Gesellschaft Mit Beschrã¤Nkter Haftung (Bundesrepublik Deutschland)
• Inventors: Rech, Bernd, Stangl, Rolf
• Granted Patent: US 8,395,043 B2
• Time in Patent Office: Days
• US Class Current: 136/256
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for back-contact solar cells
• CPC Class Codes: H01L 31/022458 for emitter wrap-through [EWT] type solar cells, e.g. interdigitated emitter-base back-contacts
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/186 Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A solar cell includes a photoactive, semiconductive absorber layer configured to generate excess charge carriers of opposed polarity by light incident on a front of the absorber layer during operation. The absorber layer is configured to separate and move, via at least one electric field formed in the absorber layer, the photogenerated excess charge carriers of opposed polarity over a minimal effective diffusion length L_eff,min. The absorber layer has a thickness L_x of 0<L_x≦L_eff,min. First contact elements are configured to remove the excess charge carriers of a first polarity on a rear of the absorber layer. Second contact elements are configured remove the excess charge carriers of a second polarity on the rear of the absorber layer. At least one undoped, electrically insulating second passivation region is disposed in an alternating, neighboring arrangement with a first passivation region on the rear of the absorber layer.

Claims

1-19. -19. (canceled)

20. A solar cell, comprising:

a photoactive, semiconductive absorber layer configured to generate excess charge carriers of opposed polarity by light incident on a front of the absorber layer during operation, the absorber layer being configured to separate and move, via at least one electric field formed in the absorber layer, the photogenerated excess charge carriers of opposed polarity over a minimal effective diffusion length L_eff,min in the absorber layer, the absorber layer having a thickness L_x of 0<

L_x≦

L_eff,min;

first contact elements configured to remove the excess charge carriers of a first polarity on a rear of the absorber layer which faces away from the light incident during operation;

second contact elements configured remove the excess charge carriers of a second polarity, opposite to the first polarity, on the rear of the absorber layer, a distance L_y between a respective one of the first contact elements and a respective one of the second contact elements being 0<

L_y≦

2 L_eff,min;

at least one undoped, electrically insulating first passivation region disposed on the rear of the absorber layer, each of the at least one first passivation region including a first contact opening configured for connection of a respective one the first contact elements and including a first non-semiconductive material having a surface charge of the first polarity sufficient to cause a band bending of the absorber layer in a first direction until degeneration is at least substantially achieved, and

at least one undoped, electrically insulating second passivation region disposed in an alternating, neighboring arrangement with the at least one first passivation region on the rear of the absorber layer, each of the at least one second passivation region including a second contact opening configured for connection of a respective one of the second contact elements and including a second non-semiconductive material having a surface charge of the second polarity sufficient to cause a band bending of the absorber layer in a second direction opposite to the first direction until degeneration is at least substantially achieved.

21. The solar cell according to claim 20, wherein the first and second contact elements have at least one of a point-like and a strip-like design.

22. The solar cell according to claim 21, wherein the first and second contact elements include two metals having different work functions based on the polarity of the excess charge carriers to be dissipated.

23. The solar cell according to claim 20, wherein the first and second contact openings are respectively disposed at least in a region of centroids of the first and second passivation regions.

24. The solar cell according to claim 20, wherein the first and second contact openings include a plurality of randomly distributed contact openings having nanoscale dimensions respectively disposed in the first and second passivation regions.

25. The solar cell according to claim 20, further comprising a planar passivation layer disposed on the front of the absorber layer.

26. The solar cell according to claim 25, wherein the planar passivation layer includes alternating electrically insulating first and second passivation areas having a high surface charge, the first and second passivation areas of the planar passivation layer respectively having an opposed polarity and an opposite arrangement to the first and second passivation regions disposed on the rear of the absorber layer.

27. The solar cell according to claim 20, wherein at least one of the first and the second passivation regions includes at least one of a planar and a structured electrically conductive intrinsic passivation layer which contacts the absorber layer in a region of at least one of the first and the second contact openings.

28. The solar cell according to claim 27, wherein the absorber layer is doped and the at least one of a planar and a structured electrically conductive intrinsic passivation layer includes additional, oppositely doped emitter layers that are at least one of heterogeneously applied and diffused.

29. The solar cell according to claim 27, wherein the absorber layer is doped and the at least one of a planar and a structured electrically conductive intrinsic passivation layer includes additional, identically doped, heterogeneously applied hack surface field (BSF) layers that are diffused at least one of locally and over an entire surface of the at least one of a planar and a structured electrically conductive intrinsic passivation layer.

30. The solar cell according to claim 27, wherein the at least one of a planar and a structured electrically conductive intrinsic passivation layer includes intrinsic a-Si:

H.

31. The solar cell according to claim 20, further comprising a narrow, thin, electrically insulating third passivation region without a high surface charge disposed between the first and the second passivation regions.

32. The solar cell according to claim 20, wherein the absorber layer is doped and at least one of the first and the second contact openings include additional, oppositely doped emitter layers that are at least one of heterogeneously applied and diffused, and which have a same surface charge as the doped absorber layer.

33. The solar cell according to 32, wherein the additional, oppositely doped emitter layers extend from the at least one of the first and the second contact openings to a respective one of the first and the second passivation regions without mutual contact with one another.

34. The solar cell according to claim 20, wherein the absorber layer is doped and at least one of the first and the second contact openings include additional, identically doped back surface field (BSF) layers that are at least one of heterogeneously applied, locally diffused and planarly diffused, and which have an opposite surface charge to the doped absorber layer.

35. The solar cell according to 34, wherein the additional, identically doped BSF layers extend from the at least one of the first and the second contact openings to a respective one of the first and the second passivation regions without mutual contact with one another.

36. The solar cell according to claim 20, wherein at least one of the first and the second contact openings include a feedthrough extending to the front of the absorber layer, a coating of the feedthrough and the absorber layer being of a same material as at least one of the first and the second passivation regions.

37. The solar cell according to claim 20, wherein the absorber layer includes at least one of intrinsic and doped silicon, the first and the second passivation regions respectively include aluminium oxide (AlO) with a high negative surface charge and silicon nitride (SiN) with a high positive surface charge, and the first and the second contact openings include at least one of a metal and a transparent conductive oxide (TCO).

38. A method for producing a solar cell including a plurality of randomly distributed contact openings in first and second passivation regions, the method comprising:

depositing a first, electrically insulating passivation layer having a high surface charge of a first polarity with a layer thickness d₁ directly over a rear surface of an absorber layer of the solar cell;

structuring the first, electrically insulating passivation layer into the second passivation regions of the first polarity;

.

depositing a second, electrically insulating passivation layer having a high surface charge of a second polarity, opposite to the first polarity, with a layer thickness d₂ directly onto the rear surface of the absorber layer and directly onto the second passivation regions;

structuring the second, electrically insulating passivation layer into the first passivation regions;

depositing a matrix including a plasma-etch-resistant material over an entire surface of each of the first and the second passivation regions; and

structuring the matrix;

partially etching off the matrix so as to remove the matrix completely at randomly distributed points; and

selectively etching the solar cell using a plasma that corrodes the first and second passivation regions and does not corrode the matrix, wherein the layer thicknesses d₁, d₂ of the first and second passivation regions are selected based on respective etching rates of the first and second passivation regions so as to form the plurality of randomly distributed contact openings extending to the absorber layer.

39. The method according to claim 38, wherein the matrix includes ZnO.