WO2005036655A1

WO2005036655A1 - Photovoltaic solar cells comprising metal nanoemitters and method for the production thereof

Info

Publication number: WO2005036655A1
Application number: PCT/DE2004/002228
Authority: WO
Inventors: Hans-Joachim Lewerenz
Original assignee: Hahn-Meitner-Institut Berlin Gmbh
Priority date: 2003-10-09
Filing date: 2004-10-05
Publication date: 2005-04-21
Also published as: DE10347401B4; DE10347401A1

Abstract

According to prior art, in order to improve conversion efficiency of solar energy in electric current for a solid body solar cell, the continuous metal emitter film is subdivided into a plurality of nanoemitters in order to reduce shadowing and recombination loss. The nanoemitters comprising, respectively, a spatial-charging area of extension w in the semi-conductor layer to which the minority charge carrier migrate along a diffusion length L, are arranged in a dotted manner on the surface of the absorbing semi-conductive layer. In order to improve efficiency further, the inventive photovoltaic solar cell (SZ) is provided with nanoemitters (NE) which are embodied in a needle or rib type manner and are separated from each other at a regular distance D≤ √2L and having a penetration depth T ≥ dHL - L/2 + w in the semiconductor layer (HL). Shadowing, recombination and use of material can be minimised during the simultaneous use of qualitative reduced-value semi-conductor material, thereby optimising efficiency by virtue of the precise dimensioning of the metal nanoemitters (NE) and the expansion thereof in the semi-conductor layer (HL) for complete accumulation of the light-induced charge carrier. A preferred production method can be carried out continuously using a humid or electro or photoelectrochemical technique, thereby conserving energy and reducing costs in the low temperature range, especially when producing large, flat solar cells.

Description

Photovoltaic solar cell with metallic nano-emitters and manufacturing process.

description

The invention relates to a photovoltaic solar cell with an electrical solid-state contact between a semiconductor layer with a layer thickness dm. and a multiplicity of metallic nano-emitters embedded in an electrically insulating oxide layer arranged on the semiconductor layer, each with a space charge zone of extension w in the semiconductor layer to which the minority charge carriers migrate over a diffusion length L, and one transparent conductive layer that is electrically insulated from the semiconductor layer by the oxide layer as well as front and rear contacts and a method for producing such a solar cell.

When it comes to photovoltaic power generation, the efficiency of converting solar radiation into electrical power is of crucial importance. In order to obtain an optimal yield, in addition to a reduction in the reflection and recombination losses, a reduction in the shading losses and an improvement in the light collection are particularly sought. Shadowing of the light irradiation surface occurs in particular through the front contacts, through the transparent, electrically conductive conductive layer, for example ITO, and through the emitter layer in Schottky-type solar cells with a solid-state contact between the doped semiconductor layer and a rectifying metal layer. The same applies to simple pn junctions between a normally doped and a highly doped semiconductor layer. For efficient photovoltaic energy conversion between solid-state contacts, the emitter layer can be applied as a closed layer, but in a very small layer thickness to the semiconductor layer working as the base or absorber. Vacuum can do the same PVD, and diffusion processes are applied. Furthermore, point contact solar cells are proposed which have an optimized point contact pattern on the back of the solar cells in direct contact with highly doped storage zones in the absorber layer (compare publication I by J. Zhao et al .: "22.7% efficient perl Silicon solar cell module with a textured front surface" , 26th PVSC, 1197, Anaheim, CA, pp 1133-1136, Fig. 2. This publication also discloses pyramid-like structuring of the cell surface in the region of the uppermost layers, including the emitter layer, in order to reduce reflections. structuring, the depth of penetration of the emitter layer into the correspondingly conformally structured semiconductor layer is only relatively small. The front contacts are applied as narrow strips as possible in order to reduce the shading losses and thus increase the conversion efficiency of the solar cell d doped below the contact strips higher than in the area of direct sunlight. From WO 02/103810 A1 it is also known to design the front contacts as wedge-shaped trenches to reduce the shading losses, which are narrower than simple contact strips but have a greater depth of penetration into the emitter and the semiconductor layer underneath (buried contact). However, a significant improvement in efficiency cannot be achieved, since the main light collection in the area of the contact-free emitter-absorber transition takes place without increased penetration depth. From Japanese abstract JP 04015963 A it is also known to store individual emitter regions in the depth of the absorber layer in order to improve efficiency in order to reduce recombinations (buried island areas). However, each emitter region is connected to a front contact strip via its own contact hole. A similar procedure for the semiconductor material is also known from DE 198 37 365 A1, which teaches the incorporation of clusters into the active absorber layer in order to provide additional charge carriers. The optical properties of the semiconductor are thereby changed in order to use further wavelength ranges of sunlight. The However, clusters grow self-organized from defects and are therefore difficult to control in terms of distribution and size.

The prior art on which the present invention is based is described in the publication II by H. Tsubomura et al .: “Effect of Microscopic Disconnectivity of Metal Overlayers on the Photovoltages in Metal-Coated Semicon- ductor-Liquid Junction Photoelectrochemical Cells for Efficient Solar Energy Conversion ". The main aim of this publication is to improve the catalysis of the photoelectrochemical process in an electrolytic solar cell (PEC). The application of catalytically active metal films leads to solid-state contact, which is also in the form of a Schottky contact is necessarily inferior to a p / n semiconductor contact, since it leads to increased losses due to charge carrier recombination. However, the size of the leakage currents occurring at the semiconductor / metal contact can be reduced if the continuous metal film is very small (diameter a few nrn ) Metal islands as metallic nanoemitters that cover only a small part of the surface. These metal point contacts are produced by etching a metal film on a silicon diode. However, this immediately forms an oxidic insulation layer in an aqueous electrolyte. The semiconductor / electrolyte contact is thus replaced by a pure solid-state contact in which, in addition to the catalytically active metal islands, an insulating oxide layer covers most of the surface. In the discussion point of his publication, Tsubomura then states that it is also possible to transfer the procedure for reducing the leakage currents to a solid-state solar cell if a transparent conductive layer is applied to the oxide layer instead of the redox electrolyte solution. However, Tsubomura does not specify a dimensioning rule for the size and distribution of the metal islands. The islands lie at a relatively large distance from one another (four times the diameter) on the surface of the semiconductor layer, so that the achievable efficiency is not yet fully satisfied, particularly in solid-state solar cells. The object of the present invention is therefore to be seen in developing the photovoltaic solar cell described at the outset in such a way that a further improvement in efficiency in photovoltaic energy conversion can be achieved with two solid-state contacts. A preferred method for producing such a highly efficient solid-state solar cell is said to be inexpensive and energy-saving.

The solution to this problem in a generic solar cell with an electrical solid-state contact between a semiconductor layer with a layer thickness dm and a large number of metallic nanoemitters, each with a space charge zone of the extent w in the semiconductor, to which the minority charge carriers migrate in the semiconductor layer over a diffusion length L, It is therefore provided according to the invention that the metallic nano-emitters are needle-shaped or rib-shaped and have a uniform distance -D ≤ V2L to one another and a depth of penetration

T ≥ d _HL - + w in the semiconductor layer.

In the solid-state solar cell according to the invention, metallic nano-emitters are used with one of the minority charge carriers or their

Diffusion length used in the semiconductor as a relevant parameter-dependent, predetermined homogeneous density distribution, whereby a minimal

Material use with optimal shading of the absorbent

Semiconductor layer can be guaranteed by the second solid-state contact and minimal recombination losses. Thus, a high

Implementation efficiency in electricity collection can be achieved. This is increased significantly in the invention in that the metallic

Nanoemitters are now three-dimensional in the shape of needles or ribs and extend deep into the semiconductor layer. The metallic nano-emitters in the prior art, however, are two-dimensional point-shaped pronounced and are only on the surface of the absorbing semiconductor. The penetration depth of the metallic nanoemitters in the invention is also dependent on the relevant parameters diffusion length L, space charge zone w and layer thickness dm _. the semiconductor layer can be calculated exactly and can thus be optimized. According to an advantageous embodiment of the invention, the metallic nanoemitters can have lateral branches in the semiconductor layer, so that a tree-like structure is produced. Furthermore, they can run obliquely in the semiconductor layer, so that all layer areas are optimally reached by the nanoemitters. Thus, in the solar cell according to the invention, the entire layer thickness of the absorbing semiconductor layer up to the back contact can be used for energy conversion, which leads to optimal efficiency in the collection of the light-generated minority charge carriers while avoiding recombination effects. In the case of punctiform nanoemitters, only a penetration depth depending on the simple diffusion length can be achieved, so that for the complete detection of the absorbing semiconductor layer, it must be made correspondingly thin. On the other hand, for an approximately 90 percent light collection, the layer thickness of the semiconductor layer must again be greater than three times the absorption length 1 / α with the absorption coefficient α, so that overlapping boundary conditions can result, which can lead to lower efficiency.

In the case of the invention, the depth detection of the absorbing semiconductor layer also enables the use of semiconductor material which is not of first-class quality, that is to say such material with a smaller diffusion length of the minority charge carriers, which results in significant cost savings. Furthermore, crystalline materials and epitaxially grown layers of, for example, Si, GaAs and InP can be made significantly thinner, since in the solar cell according to the invention the sensitivity to red when collecting near the back contact is greatly improved. This applies in particular if, according to an embodiment of the invention, on the back of the semiconductor layer a reflective layer is applied to the back contact. A further improvement of the conversion efficiency results according to a next invention, if an anti-reflection layer is applied to the transparent conductive layer. This can be, for example, a layer with a positive or negative pyramid structure or some other microstructuring that reliably captures the incident light and directs it to the absorber.

Using a metal for the nanoemitter creates a Schottky contact. The metal must be selected so that a rectifying contact is formed. A metal with a low work function must therefore be selected for p-doped semiconductor material to generate the photocurrent, and a metal with a higher work function for n-doped semiconductor material. Schottky solar cells have the advantage of simply forming a diode contact by applying a metal to the semiconductor layer. There is no need for complex and complicated doping processes and stability studies in the differently doped areas. At this point, however, it should be noted that the nanoemitters can also consist of semiconductor material. When using a highly doped semiconductor material as a nanoemitter, an efficient pn junction is formed if the semiconductor materials are doped accordingly in opposite directions. Due to the size of the nanoemitter in the nm range (preferably between 10 nm and 100 nm) in the invention, the shading of the absorbing semiconductor layer and the material consumption can be kept particularly low. Dimensions of the nanoemitter down to the μm range are also possible. The nanoemitters can be grown directly on the semiconductor layer or applied as a colloid. On the semiconductor layer, they are surrounded by the oxide layer and can protrude slightly above it. As a result, the nanoemitters can extend into the transparent conductive layer applied to the oxide layer. The absorbing semiconductor can, but need not, be doped (p- or n-doped). Highly pure, so-called "Floatzone" (FZ) silicon is nominally undoped, but slightly n-conductive; it is used for high-performance solar cells used. So-called "Czochralski" (CZ) silicon does not achieve the quality of FZ silicon, so doping is necessary. The oxide layer can be a natural oxide, for example SiO ₂ , which is grown anodically by exposure or application of a potential. Further information on the structure can be found in the method options for production described below.

It is also an object of the present invention to provide a method for producing a photovoltaic solar cell with the structure claimed, which is to be inexpensive and energy-saving. This object is achieved by a preferred process with the following process steps:

Wet chemical or electrochemical or photoelectrochemical application of an electrically insulating oxide layer of high electronic quality to a semiconductor layer,

Structuring of the oxide layer by removing the oxide layer in the form of points or lines at the locations provided for arranging the nanoemitters,

Wet-chemical or electrochemical or photoelectro-chemical needle or rib-shaped etching of the structure in the oxide layer into the semiconductor layer,

• light-induced or potential-controlled electrochemical deposition of metal into the structure in the oxide layer and in the semiconductor layer from a redox electrolyte, • wet-chemical or electrochemical or photo-electrochemical application of a transparent conductive layer on the oxide layer and

• Application of front and back contacts.

In particular, according to a preferred method continuation, a likewise wet-chemical or electrochemical or photo-electrochemical structuring of the oxide layer can be provided, so that the Can manufacturing process of the solar cell throughout wet chemical or electro ^¬ chemical or photoelectrochemical leads in the low temperature range Runaway ^¬. This does not apply to the final application of the front contacts, for example in the form of contact fingers, which is usually carried out by vapor deposition. However, this is a standardized process that does not increase the procedural effort and costs. The process parameters during production, however, have a significant influence on this. Significant process improvement can be achieved here by avoiding high temperatures and process changes provided by the invention. Here, wet chemical / electrochemical processes can easily be scaled up and used to produce large areas, as is known from electroplating.

It is important for the increase in efficiency in the previously described solar cell with specially designed metallic nanoemitters that the exact positioning and compliance with the dimensions of the nanoemitters is ensured by the precise structuring of the oxide layer and the semiconductor layer. In technological applications, the structuring of the oxide layer can be carried out, for example, with electron beam lithography or with ion beam etching (FIB focused ion beam etching). Alternatively, but also without the use of high temperatures, the structuring of the oxide layer, which can be ZnO, SnO ₂ or ITO, for example, the structuring of the oxide layer can also be carried out by means of scanning probe microscopy in accordance with a next process continuation, whereby an even more precise and controlled Determining the nano-emitter positions is possible. There are basically two options here. On the one hand, the oxide layer can be scanned in a selected surface area with an AFM (atomic force microscopy) with a sufficiently high contact force. As a result of this process, the oxide layer is pushed aside and the semiconductor layer underneath is exposed. On the other hand, an identification with a diamond needle can be carried out by means of AFM the oxide layer is pierced to make contact. According to another further development of the invention, the mechanical structuring of the oxide layer can also have a plurality of indications impressed in parallel for structuring a large-area oxide layer. In this so-called “millipede technique”, a large number of identifications (a few hundred) are carried out at the same time using, for example, AFM (atomic force microscopy). In particular for large-scale applications, such structuring in connection with the continuous electrochemical / wet-chemical production that can also be carried out on a large scale is therefore In order to be able to heal any deformations that may arise during the indentation or scratching, the structures can then, according to a further method, gently chemically or electrochemically etch the locations of the removed oxide layer and subsequently apply a potential, current and charge-controlled application electrically insulating anodic oxide layer (1 to 3 atomic layers) are subjected to the structure in the semiconductor layer before the deposition of metal.This process serves to suppress recombination processes on and in d he environment of defects.

After the surface structuring of the oxide layer, there is a process step for deepening the structures into the semiconductor layer. This is done by wet chemical or electrochemical or photoelectrochemical etching. Starting from point structures in the oxide layer, needle-shaped or pore-shaped depressions result. Linear structures in the oxide layer are deepened into ribs or trenches. The etching is a simple but precise process since the surface of the semiconductor layer that is not to be etched is reliably protected by the oxide layer. The etching depth can be precisely determined using the appropriate material and time parameters. The same applies to the possible etching of lateral branches which can originate from the central needle-shaped or rib-shaped etching recess, and to depressions which run obliquely in the semiconductor layer. An important process step is the subsequent filling of the needle or rib shaped depressions and also possible lateral branches, that is, the local deposition of the metallic nano-emitters. Here, a light-induced or potential-controlled electrochemical deposition of metal is carried out. The separation in the side branches can be guaranteed. When deposited by light, the metal is chosen so that a rectifying Schottky contact is created. The semiconductor can be p, n or undoped. In the case of n semiconductors, the metal is deposited in the dark by forming negative accumulation layers. In order to avoid repetition, reference is made to the special description part in connection with the corresponding figures with regard to the more precise procedure for light-induced deposition. An alternative preparation can be carried out by introducing a metallic colloid into the needle-shaped or rib-shaped depressions in the semiconductor layer. After the colloid has been introduced, the exposed surface areas of the semiconductor layer are electrochemically oxidized, so that the desired nanoemitter structure is embedded in an oxide layer there. Process steps following the generation of the nanoemitters can comprise, in accordance with further embodiments, the application of a reflective layer on the rear side of the semiconductor layer and / or the application of an antireflection layer on the transparent conductive layer. Both additional layers serve to further improve efficiency, as already explained above in connection with the solar cell according to the invention.

Forms of embodiment of the invention are explained in more detail below with the aid of the schematic figures for their further understanding. It shows:

1 shows an embodiment of a solar cell according to the invention in cross section,

FIG. 2 shows an energy band location diagram for the light-induced local deposition of the nanoemitters in the area of the nanoemitters, 11

3 shows an energy band location diagram for the light-induced local deposition of the nano-emitters in the region of the oxide layer, and FIG. 4 shows a detail for the light-induced deposition of the nano-emitters.

1 shows a photovoltaic solar cell SZ with an electrical solid-state contact between a doped semiconductor layer HL with a layer thickness d _H ι_ and a large number of metallic nano-emitters NE embedded in an electrically insulating oxide layer OS on the surface of the semiconductor layer HL. With a corresponding choice of metal, a rectifying Schottky contact with the semiconductor layer HL results. The rectifying nanoemitters NE generate a space charge zone (depleted area) of the dimension w in the semiconductor layer HL. Upon exposure, when the incident light energy hv is greater than the work function E _{g of} the charge carriers, electron-hole pairs are generated in the semiconductor layer HL. The minority charge carriers (electrons for p-silicon as semiconductors, holes or “defect electrons” for n-silicon) migrate with a diffusion length L to the metallic nano-emitters NE which act as a sink. A particularly efficient solar energy conversion is achieved if the distance D of the metallic Nanoemitter NE applies: D ≤ ΪL

In the case of an equality, the optimum distance between the metallic nanoemitters NE is achieved, which ensures minimal shading and minimal use of materials. If the distance D falls below the upper limit, a corresponding overlap is given while accepting a certain additional consumption of material, but this ensures reliable utilization of the semiconductor layer HL in the corresponding radial plane. If the metallic nanoemitters NE were arranged exclusively on the surface of the semiconductor layer HL, however, the efficient use would be limited to the uppermost layer of the semiconductor layer HL. To be a complete To achieve utilization, the layer d _{HL of} the semiconductor layer HL should therefore not be greater than the diffusion length L of the respective minority charge carriers. In the solar cell SZ according to the invention, however, the metallic nano-emitters NE also extend into the depth of the semiconductor layer HL, so that the advantageous reverse case now arises. Depending on the layer thickness d _H ι_ of the semiconductor layer HL, the diffusion length L of the minority charge carriers and the extent w of the space charge zone, a penetration depth T is defined for which:

T ≥ d _HL - + w

In the case of equality, this again results in the optimal utilization of the semiconductor layer HL up to the back contact RK of the solar cell SZ and a safety coverage if the limit value is undershot. A dependence of the layer thickness dm. the semiconductor layer with the absorption coefficient α or the absorption length 1 / α, in the form that the layer thickness d _H ι_ of the semiconductor layer must be greater than 3 / α in order to achieve optimum layer utilization with purely crystalline semiconductor material, is then not given ,

The metallic nanoemitters NE are on the surface of the semiconductor. HL is not surrounded by a closed oxide layer OS, the layer thickness of which only has to be dimensioned to such an extent that reliable insulation of the metallic nanoemitters NE from one another and between the semiconductor layer HL and a transparent conductive layer TCO applied to the oxide layer OS is ensured. The metallic nanoemitters NE can protrude somewhat into the transparent conductive layer TCO. Due to the division of the areas between the nanoemitters NE, such a solar cell SZ can be referred to as a compartment solar cell. The current is collected via front contacts FK, for example in the form of strips or fingers, which are applied to the transparent conductive layer TCO. Here is one too To strive for minimal shading. To further improve the conversion efficiency, an antireflection layer on the top and a reflective layer on the back can be provided before the back contact of the solar cell SZ.

For the preparation and modification of the oxide layer OS, wet-chemical thin oxides with high electronic quality of the oxide / semiconductor interface can be deposited. There are further possibilities in the production of anodic oxides with subsequent post-drying or in the use of electropolished oxides with subsequent post-drying. Furthermore, thermally produced and natural oxides can be used. The oxide structuring is preferably carried out mechanically, for example by means of AFM by pushing aside or penetrating the oxide layer OS.

For the possibility of local deposition of nano-emitters NE made of metal on a semiconductor material, here p-Si, for the production of Schottky contacts by means of a photo-induced electrochemical process, the energetic situation at the contact p-Si / metal / electrolyte with cathodic polarization of the silicon Si considered. A distinction is made between areas of the Si surface that are covered and free of oxide. The respective light-induced processes are shown in energy band-location diagrams (energy E over location x, E _F Fermi level). FIG. 2 shows the behavior of an uncovered part of the semiconductor layer HL for the subsequent positioning of a metallic nanoemitter NE with cathodic polarization (applied voltage V _a ) and exposure (hv). The light-generated excess charge carriers migrate either to the back contact RK (holes (+)), which is flat in the exemplary embodiment, or to the surface (electrons (-)). The electrons can with a suitable energetic position of the lower edge of the conduction band (EL) and a metallic one

Redoxpaares (Me ^{z + / 0} ) the reaction

Me ^{z +} + ne ^" → Me ^{(z" n) +} drain. The metallic phase is formed for n = z. For monovalent metal ions, for example: Ag ⁺ + e ^" → Ag °.

This leads to metal deposition at the free surface and depth regions of the semiconductor layer HL and thus to the formation of the metallic nanoemitter NE. Equivalently, metal deposition can also be effected on n-Si by cathodic polarization in the dark (unexposed). In this case, the conduction band electrons are to be regarded as accumulated majority charge carriers. The light-induced deposition in p-semiconductors and deposition in the dark on n-semiconductors with cathodic (negative) potential represents - in comparison to the flat band situation - a very gentle and particularly well-defined process in comparison to vapor deposition, sputtering or etching of metal films.

FIG. 3 shows the corresponding behavior for oxide-covered areas on the semiconductor layer HL. For layer thicknesses d _{OX of} the oxide layer that are significantly larger than the so-called tunnel thickness (dox ≥ 3 nm), the light-induced electrons are no longer transferred into the electrolyte. Rather, there is "trapping" at traps on the surface of the semiconductor layer HL and recombination. However, if the electronic quality of the Si / oxide interface is sufficiently high, a charge carrier drift to the metallic nanoemitters NE takes place. This is shown in FIG.

The orderly exposure of contact areas on and in the semiconductor layer HL after the formation of a thicker (for example 10 nm) anodic oxide layer OS, the subsequent deposition of metallic nanoemitters NE for producing rectifying nanocontacts and the application of, for example, SnO ₂ as a transparent conductive layer TCO enables through - Common manufacture of a completely wet and electrochemically prepared solar cell at low temperature, which results in an energy-saving and inexpensive process.

LIST OF REFERENCE NUMBERS

D distance of the nanoemitters d _H [_ layer thickness of the semiconductor layer d _0x layer thickness of the oxide layer

FK front contact

HL semiconductor layer

L Diffusion length of the minority charge carriers NE nanoemitter

OS oxide layer

RK back contact

SZ solar cell

T penetration depth of the nanoemitter TCO transparent conductive layer w expansion of the space charge zone

Claims

claims

1.Photovoltaic solar cell with an electrical solid-state contact between a semiconductor layer with a layer thickness d _HL and a multiplicity of metallic nano-emitters embedded in an electrically insulating oxide layer arranged on the semiconductor layer, each with a space charge zone of the extent w in the semiconductor layer to which the minority charge carriers are connected via a Migrate diffusion length L, and a transparent conductive layer electrically isolated from the semiconductor layer by the oxide layer, as well as front and back contacts, characterized in that the metallic nano-emitters (NE) are needle-shaped or rib-shaped and have a uniform distance D ^{≤ "} v ² ^ from one another and an intrusion

have deep T ≥ d _HL - + w in the semiconductor layer (HL).

2. Photovoltaic solar cell according to claim 1, characterized in that the metallic nano-emitters (NE) in the semiconductor layer (HL) have lateral branches and / or run obliquely in the semiconductor layer (HL).

3. Photovoltaic solar cell according to claim 1 or 2, characterized in that a reflective layer is applied to the back of the semiconductor layer (HL) before the back contact (RK).

4. Photovoltaic solar cell according to one of claims 1 to 3, characterized in that an anti-reflection layer is applied to the transparent conductive layer (TCO).

5. Method for producing a photovoltaic solar cell with an electrical solid-state contact between a semiconductor layer with a layer thickness dm. and a multiplicity of metallic nano-emitters embedded in an electrically insulating oxide layer arranged on the semiconductor layer, each with a space charge zone of extension w in the semiconductor layer to which the minority charge carriers migrate over a diffusion length L, and one transparent conductive layer that is electrically insulated from the semiconductor layer by the oxide layer as well as front and rear contacts, the nano-emitters being needle-shaped and uniform

Distance ö ≤ 2L to each other and a penetration depth T ≥ d _HL - + w into the

Have semiconductor layer, in particular according to claim 1 or 2, characterized by the method steps:

Wet-chemical or electrochemical or photo-electrochemical application of an electrically insulating oxide layer (OS) of high electronic quality to a semiconductor layer (HL),

• Structuring of the oxide layer (OS) by removing the oxide layer (OS) in the form of points or lines at the locations provided for arranging the nano-emitters (NE), • Wet-chemical or electrochemical or photo-electrochemical needle-like or rib-shaped etching of the structure in the oxide layer (OS) in the semiconductor layer (HS) into it,

Light-induced or potential-controlled electrochemical deposition of metal into the structure in the oxide layer (OS) and in the semiconductor layer (HL) from a redox electrolyte,

• wet chemical or electrochemical or photoelectrochemical application of a transparent conductive layer (TCO) on the oxide layer (OS) and

• Application of front and rear contacts (FK, RK).

6. The method according to claim 5, characterized by a likewise wet chemical or electrochemical or photoelectrochemical structuring of the oxide layer (OS), so that the manufacturing process of the solar cell (SZ) is carried out consistently wet chemical or electrochemical or photoelectrochemical in the low temperature range.

7. The method according to claim 5, characterized by structuring the oxide layer (OS) by means of scanning probe microscopy.

8. The method according to claim 7, characterized by a parallel stamping of a plurality of indications for structuring a large-area oxide layer (OS).

9. The method according to any one of claims 5 to 8, characterized by

Potential, current and charge-controlled application of an electrically insulating anodic oxide layer to the structure in the semiconductor layer (HS) before the deposition of metal.

10. The method according to any one of claims 5 to 9, characterized by applying a reflective layer on the back of the semiconductor layer (HL) and / or an anti-reflection layer on the transparent conductive layer (TCO).