Method For Producing a Solar Cell, in Particular a Silicon Thin-Film Solar Cell

Abstract

A method for producing a solar cell, in particular a silicon thin-film solar cell, wherein a TCO layer (3) is applied to a glass substrate (1) and at least one silicon layer (4, 5) is applied to the TCO layer (3). Before the TCO layer (3) is applied, electron radiation is applied to the glass substrate (1), such that a light-scattering layer (2) of the glass substrate (1) is produced, to which light-scattering layer the TCO layer (3) is applied. Alternatively or additionally, a first silicon layer (4) may be applied to the TCO layer (3), a laser radiation or electron radiation may be applied to the first silicon layer (4), and a second silicon layer (5) may be applied to the irradiated first silicon layer (4).

Claims

1. A method for producing a silicon thin-film solar cell, comprising the following method steps: depositing a TCO layer (3) on a glass substrate (1); depositing a first silicon layer (4) on the TCO layer (3): exposing the first silicon layer (4) to laser radiation or electron radiation; and depositing a second silicon layer (5) on the irradiated first silicon layer (4); wherein the second silicon layer (5) is deposited at temperatures below 300 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Additional features and advantages of the present invention will become apparent from the following description of preferred exemplary embodiments with reference to the appended drawings. These show in:

[0012] FIG. 1 a schematic section through a first solar cell produced by a method according to the invention;

[0013] FIG. 2 a schematic section through a second solar cell produced by a method according to the invention;

[0014] FIG. 3 a schematic section through a third solar cell produced by a method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0015] In the figures, identical or functionally identical parts or layers are provided with the same reference numerals.

[0016] In a first embodiment of the method according to the invention, a glass substrate 1 is heated to a temperature between 200 C. and 700 C., preferably to a temperature between 300 C. and 500 C., for example, to a temperature of 400 C. and the surface which is arranged at the top of FIG. 1 is exposed to electron radiation. In particular, an electron beam having a line-shaped cross-section is moved across the surface of the glass substrate 1 perpendicular to the direction of the line.

[0017] The irradiation with the electron beam accompanied by heating partially causes lighter constituents in the glass in a layer 2 of the glass substrate to diffuse out of the surface. These constituents may be, for example, Na.sub.2O, K.sub.2O, MgO or CaO. This outdiffusion of constituents of the glass produces light-scattering structures in the layer 2.

[0018] In a further method step, a TCO layer 3 which may serve as a first electrode of the solar cell is deposited on this layer 2. This may be done using conventional deposition methods, for example sputtering. In particular, the material to be vaporized may be vaporized with an electron beam. The glass substrate 1 may be at room temperature during the deposition of the TCO layer 3.

[0019] For example, ZnO may be used as TCO material. However, other TCO materials, in particular other mixed oxides of tin or zinc, such as ITO, FTO, AZO and ATO may be used.

[0020] In a further method step, the TCO layer 3 is exposed to laser radiation for the purpose of reducing the resistance of the TCO layer 3. In this case, a laser beam with a line-shaped cross-section can be used which is moved across the surface of the TCO layer 3 perpendicular to the direction of the line. The glass substrate 1 may be at room temperature during the exposure to the laser radiation.

[0021] In a subsequent process step, a relatively thin first silicon layer 4 is deposited on the TCO layer 3 processed in this manner. The first silicon layer 4 may have a layer thickness of less than 3.0 m, in particular a layer thickness of less than 2.0 microns, preferably a layer thickness of less than 1.0 microns, for example, a layer thickness between 0.5 m and 1.0 m.

[0022] The first silicon layer 4 can be deposited by using conventional methods, for example, sputtering. In particular, the silicon to be vaporized can be vaporized with an electron beam. The glass substrate 1 may be at room temperature when the first silicon layer 4 is deposited.

[0023] In a further process step, the first silicon layer 4 is exposed to laser radiation or electron radiation, wherein in particular the first silicon layer 4 can be restructured, which improves its adhesion to the TCO layer 3. In particular, the first silicon layer 4 is scratch-resistant following this laser irradiation or electron irradiation.

[0024] In this case, a laser beam or an electron beam with a line-shaped cross-section can be used which is moved across the surface of the first silicon layer 4 perpendicular to the direction of the line. The glass substrate 1 may also be at room temperature during the exposure to laser radiation or electron radiation.

[0025] In a subsequent process step, a comparatively thick second silicon layer 5 is deposited on the first silicon layer 4. The second silicon layer 5 can have a layer thickness between 2.0 m and 20 m, in particular a layer thickness between 3.5 m and 15 m, preferably a layer thickness between 5 m and 10 m.

[0026] The second silicon layer 5 can be deposited with conventional methods, for example sputtering. In particular, the silicon to be vaporized can be vaporized with an electron beam. The glass substrate 1 can be at room temperature when the second silicon layer 5 is deposited.

[0027] The second silicon layer 5 is exposed in a further process step to laser radiation or electron beam radiation, wherein in particular the second silicon layer 5 may be restructured from an amorphous to a polycrystalline state.

[0028] In this case, a laser beam or an electron beam with a line-shaped cross-section can be used which is moved across the surface of the second silicon layer 5 perpendicular to the direction of the line. The glass substrate 1 can also be at room temperature when the laser radiation or electron beam radiation is applied.

[0029] In a further process step, a second metallic electrode 6, which is only schematically depicted in FIG. 1, is deposited on the outer side of the second silicon layer 5. This electrode 6 may cover the entire surface of the second silicon layer 5 or may, as indicated, cover only certain areas of the second silicon layer 5.

[0030] The pretreatment of the glass substrate 1 with the electron radiation may also be omitted in a method according to the invention. FIG. 2 shows an embodiment of a solar cell where the scattering layer 2 was omitted.

[0031] In this case, the TCO layer 3 can be deposited directly on the glass substrate 1 that was not pretreated with an electron beam. Alternatively, a buffer layer may be deposited on the glass substrate 1 prior to the deposition of the TCO layer 3. This buffer layer may preferably be made of silicon dioxide, silicon nitride, or silicon carbide and may have a thickness of, for example, between 10 nm and 200 nm, in particular between 20 nm and 100 nm.

[0032] Furthermore, a buffer layer may also be deposited on a glass substrate 1 that was pretreated according to the invention with electron radiation. This buffer layer may preferably also be made of silicon dioxide, silicon nitride, or silicon carbide and may have a thickness of, for example, between 10 nm and 200 nm, in particular between 20 nm and 100 nm.

[0033] Furthermore, the silicon layer in a method according to the invention may not be composed of two sub-layers in a modular fashion, but only a single silicon layer may be provided instead. An embodiment of a solar cell is indicated in FIG. 3, which includes a scattering layer 2, but wherein the thin first silicon layer 4 was eliminated. In this case, the relatively thick silicon layer 5 is deposited according to the invention directly onto the TCO layer 3.

[0034] Every issued patent, pending patent application, publication, journal article, book or any other reference cited herein is each incorporated by reference in their entirety.