DE102008041457A1 - Photovoltaic cell for use as solar cell, solar panel or photo-electrochemical converter in open or in buildings, comprises partially transparent photoelectrode, transparent conductive coating, and intrinsically conductive layer - Google Patents

Abstract

A photovoltaic cell comprises a partially transparent photoelectrode, which is composed of a transparent electrically insulating material (1) and a transparent conductive coating (2). A p-conductive layer of nanosilicon (3), an intrinsically conductive layer of nanosilicon (4), and n-conductive layer of nanosilicon (5) are also included. A counter-electrode having a layer (6) of conductive material and an outer layer (7) are additionally provided in the photovoltaic cell. The used silicon is nanocrystalline silicon having a primary particle size of 5-200 nanometers. An independent claim is included for a method for producing photovoltaic cells, which involves: (A) preparing transparent photoelectrode by applying transparent conductive coating on transparent insulating material; and (B) applying porous layer nanocrystalline p-conductive silicon, intrinsically conductive layer of nanosilicon, n-conductive layer of nanosilicon and counter-electrode on the transparent photo electrode.

Description

The This invention relates to novel photovoltaic cells made of nanoparticulate, doped and / or undoped silicon are constructed.

The discovery of the transformation of light into electrical energy goes back to Alexandre Edmond Becquerel in 1839 [ Becquerel, AE "Le specter solaire et la constitution de la lumiere électrique." CR l'Acad. Sci., 1839-1841. ]. The basis of all photovoltaic cells (photovoltaic cells) is the separation of electrical charges by irradiation with photons of sufficient energy.

Most widespread are photovoltaic cells made of semiconductors, in which the pairs of charge carriers generated by light quanta are separated by internal electric fields or, due to the different mobilities, partly with respect to their charge centers [ Ch. Weißmantel, C. Hamann, Fundamentals of Solid State Physics, 4th Edition, Barth, Leipzig 1995. ].

For terrestrial applications have photovoltaic because of their diffusion Silicon cells have a special meaning. One differentiates monocrystalline, polycrystalline and amorphous silicon solar cells.

adversely In these embodiments, the complicated production the photovoltaic cells. In all cases there is one compact silicon layer before, depending on the manufacturing process sawed corresponding blocks, poured from a melt or pulled or from a vacuum process as a thin Layer was deposited.

For these reasons, great efforts have been made in recent years to develop photovoltaic cells with improved performance, ruggedness, and lower manufacturing costs. Examples are in the DE 44 99 682 T1 and the US 4,947,219 specified. However, the photovoltaic cells described in these patents still have disadvantages such. For example, the need for monocrystalline silicon or a complicated structure with many different materials.

task The present invention was therefore photovoltaic cells to develop with as few different ones as possible Materials can be easily made and one show high effectiveness.

It it was surprisingly found that nanoscale, crystalline silicon (nano-silicon), with elements of III., II. and the V. as well as the VI. Main group of the periodic system doped can be and suitable both in doped and undoped form is for the production of novel photovoltaic cells.

• a) das verwendete Silizium Primärpartikelgrößen im Bereich von 5–200 nm aufweist,
• b) kristallines nano-Silizium eingesetzt wird,
• c) an den beiden leitfähigen Elektroden unter dem Einfluß von Licht elektrische Energie entnommen werden kann.

The present invention therefore relates to photovoltaic cells consisting of an at least partially transparent photoelectrode A, which consists of a transparent insulating material ( 1 ), a transparent, conductive coating ( 2 ) and a p-type layer of nano-silicon ( 3 ), an intrinsically conductive layer of nano-silicon ( 4 ), an n-type layer of nano-silicon ( 5 ) and a counterelectrode B which is a layer ( 6 ) of a conductive material.
characterized in that

• a) the silicon used has primary particle sizes in the range of 5-200 nm,
• b) crystalline nano-silicon is used,
• c) electrical energy can be taken from the two conductive electrodes under the influence of light.

The present invention further provides a process for producing the photovoltaic cells according to the invention, characterized in that an at least partially transparent photoelectrode A, by applying a transparent conductive coating ( 2 ) on a transparent insulating material ( 1 ) and coating the coating ( 2 ) with a porous layer ( 3 ) of nano-silicon having electron-accepting properties, and on this photoelectro A successively an intrinsically conductive layer ( 4 ) made of nano-silicon, a layer ( 5 ) is applied from nano-silicon with electron-donating properties and a counter electrode B with a conductive layer.

Furthermore The object of the present invention is the use of photovoltaic according to the invention Cells as solar cells, solar panels or photoelectrochemical Converter.

The have photovoltaic cells according to the invention a simple structure compared to the prior art, with few different materials and low production costs improved efficiency and higher current densities.

The have photovoltaic cells according to the invention a so-called pin structure on. Here, p means doping with an element of the II. or III. Main group of the periodic table, n doping with an element of the V. or VI. Main group of the periodic table and i intrinsically conductive material.

The transparent insulating material ( 1 ) may be selected from inorganic and / or organic glasses and / or plastics and / or constitute a flexible composite system. The most important feature that must be fulfilled by this material is the transmission of the radiation, which excites a radiation-sensitive electron into the conduction band of the semiconductor. It can be advantageous if the insulating material comprises glass or plastic or a combination of glass or plastic which has a particularly high scratch resistance, since scratches on the surface of the material facing the radiation can lead to a deflection or scattering of the radiation and thus the current efficiency relative to the incident radiation can be reduced.

The transparent, conductive coating directly on the transparent material ( 2 ) must also be permeable to radiation. Preferably, the transparent conductive coating comprises a fluorine doped tin oxide, tin doped indium oxide (ITO), doped zinc oxide or thin silver layers. Particularly preferably, the coating has ITO.

That in the layers ( 3 ) - ( 5 nano silicon used in the photovoltaic cells of the present invention can be produced by means of a hot wall reactor or a microwave reactor.

The layers ( 3 ) to ( 5 ) may contain identical or but produced by different methods nano-silicon, the particle sizes are between 5-200 nm. Consequently, the layers ( 3 ) - ( 5 ) have different, but also the same particle size distributions.

In the layers ( 3 ) - ( 5 ), the nano-silicon is held together by means of at least one binder.

The invention also relates to photovoltaic cells in which, instead of three individually applied layers ( 3 ) - ( 5 ), a nano-silicon compact which was p-doped on one side and n-doped on the other side.

The counter electrode, which serves as a conductive layer ( 6 ), may have a structure constructed of metal particles or other conductive particles. Preferably, the layer ( 6 ) as particles a metal powder selected from platinum, tungsten, molybdenum, chromium, titanium an electrically conductive ceramic powder selected from fluorine or antimony doped tin oxide, ITO, doped zinc oxide, titanium nitride, titanium carbide or tungsten carbide or graphite powder, carbon black and / or an electric conductive polymer selected from polyaniline, polypyrrole, polythiophene or polyacetylene. The conductive layer of the counterelectrode preferably has a graphite powder. The conductive layer ( 6 ) has a thickness of 5 to 100, preferably from 20 to 50 microns.

It is clear to the person skilled in the art that a photovoltaic cell according to the invention also requires connections which make it possible to supply the electricity produced to a consumer. For this purpose, the photovoltaic cell has at least two terminals, wherein the one terminal has an electrically conductive connection to the conductive layer (FIG. 2 ) and the other terminal an electrically conductive connection to the electrically conductive layer of the counter electrode ( 6 ) must realize.

The photovoltaic cells according to the invention can be used as a finishing layer on the electrically conductive layer of the counterelectrode ( 6 ) an insulating coating or layer ( 7 ), which terminates the photovoltaic cell to the side of the counter electrode. The coating may, for. B. be a plastic or ceramic coating. The layer ( 7 ) can also be a glass or plastic disc, which with a plastic or ceramic mass on the layer ( 6 ) was adhered to the counter electrode. The insulating coating or layer can not only be applied to the counterelectrode but can be designed so that all sides of the photovoltaic cell, with the exception of the side facing the radiation, are coated with this coating. The coating achieves mechanical protection of the photovoltaic cell.

The photovoltaic cells according to the invention are preferably produced by a method which is characterized in that an at least partially transparent photoelectrode A, by applying a transparent conductive coating ( 2 ) on a transparent insulating material ( 1 ) and coating the coating ( 2 ) with a porous layer ( 3 ) is made of nano-silicon with electron-accepting properties, on the photoelectrode A is then successively an intrinsically conductive layer ( 4 ) made of nano-silicon, a layer ( 5 ) of nano-silicon with electron-donating properties and a counter electrode B applied. As materials for the construction of the layers and as the electrode A, the materials described above can be used.

The application of electrically conductive transparent coatings is well known and can be as described there or z. B. by gas phase separation. But it is also possible directly with an electrically conductive, transparent coating equipped insulating material ( 1 ), which is commercially available, for. B. from Pilkington under the name LOFTEC 8 is available.

On the one-sided on the material ( 1 ) applied electrically conductive layer ( 2 ), the semiconducting layer ( 3 ) applied.

The semiconductor material may, for. B. directly on the layer ( 2 ) or applied by the spin-on method. But it is also possible, a dispersion of nano-silicon, as a dispersion on the layer ( 2 ) and solidify there, z. B. by a thermal treatment. Preferably, a dispersion of the semiconductor material by brushing, knife coating, vapor deposition, sputtering, dipping, spraying or printing processes (such as, for example, letterpress printing, gravure printing, planographic printing, offset printing, screen printing, risography and pad printing, electrostatic printing, laser printers, inkjet printers) Layer ( 2 ) and then solidified by sintering at a temperature of 300-700 ° C.

The application of the following layer ( 4 ) and ( 5 ) takes place as for the layer ( 3 ).

On the layer ( 5 ), the counterelectrode ( 6 ) applied. The application of this layer can, for. B. by the same process steps as in the application of the layers ( 3 ) - ( 5 ) respectively. The application is preferably carried out by printing, in particular by the screen printing method. Particularly preferably, the catalytic intermediate layer is applied by applying a solution or dispersion. The application of the layer may in turn by brushing, knife coating, vapor deposition, sputtering, dipping, spraying or printing, a dispersion having at least one of the above for the catalytic interlayer feedstocks, and then sintering, preferably at a temperature of 300 to 700 ° C, done.

In addition, current-carrying conductor tracks and sealants can be applied to the cell surface in a structured manner, which makes the cell easier to handle and connect. Preferably, the photovoltaic cell is also sealed. This can be z. B. be done by the cell by a rear connection with a covering, z. B. selected from glass, plastic, polymers or composite material is sealed. The seal may be achieved by heating the cell to a temperature above the softening temperature of the transparent, electrically insulating material ( 1 ) and the covering material.

The photovoltaic cells according to the invention can z. B. for the production of photovoltaic cells, solar panels or photo-electrochemical converters, especially those which can be used both outdoors and in buildings, be used.

Based on 1 the photovoltaic cell according to the invention is explained in more detail by way of example.

In 1 schematically the structure of the photovoltaic cell according to the invention, consisting of a glass ( 1 ) with a conductive transparent oxide layer (TCO) ( 2 ), a p-type layer of nano-silicon ( 3 ), an intrinsically conductive layer of nano-silicon ( 4 ), an n-type layer of nano-silicon ( 5 ), a counter electrode ( 6 ) and a protective layer ( 7 ).

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4499682 T1 [0006]
• US 4947219 [0006]

Cited non-patent literature

• - Becquerel, AE "Le specter solaire et la constitution de la lumiere électrique." CR l'Acad. Sci., 1839-1841. [0002]
• - Ch. Weißmantel, C. Hamann, Fundamentals of Solid State Physics, 4th Edition, Barth, Leipzig 1995. [0003]

Claims (9)

Photovoltaic cell comprising - an at least partially transparent photoelectrode A, which consists of a transparent insulating material ( 1 ), a transparent, conductive coating ( 2 ), - a p-type layer of nano-silicon ( 3 ), - an intrinsically conductive layer of nano-silicon ( 4 ), - an n-type layer of nano-silicon ( 5 ), - a counter electrode B, which is a layer ( 6 ) of a conductive material - a cover layer ( 7 ), characterized in that - the silicon used has primary particle sizes in the range of 5-200 nm, - crystalline nano-silicon is used, - can be removed at the two conductive electrodes under the influence of light electrical energy. Photovoltaic cell according to claim 1, characterized in that the transparent insulating material ( 1 ) selected from inorganic and / or organic glasses and / or plastics and / or a flexible composite system represents. Photovoltaic cell according to claim 1 or 2, characterized in that the transparent conductive coating ( 2 ) Fluorine doped tin oxide, tin doped indium oxide (ITO), doped zinc oxide or thin silver layers. Photovoltaic cell according to at least one of claims 1 to 3, characterized in that the layer ( 6 ) of the counterelectrode has a structure composed of metal particles or other conductive particles, wherein the particles are selected from platinum, tungsten, molybdenum, chromium, titanium, titanium nitride, titanium carbide, tungsten carbide, fluorine or antimony doped tin oxide, ITO, doped zinc oxide, graphite powder, carbon black and / or an electrically conductive polymer selected from polyaniline, polypyrrole, polythiophene or polyacetylene. Process for the production of photovoltaic cells according to at least one of Claims 1 to 4, characterized in that - by applying a transparent conductive coating ( 2 ) on a transparent insulating material ( 1 ) a photoelectrode A is made onto which - a porous layer ( 3 ) of nanocrystalline, p-conductive silicon, - an intrinsically conductive layer ( 4 ) made of nano-silicon, - an n-conductive layer ( 5 ) of nano-silicon - and a counter electrode B are applied. A method according to claim 5, characterized characterized in that in addition to the cell current-carrying Printed conductors and sealants applied structured surface become. A method according to claim 5 or 6, characterized in that the photovoltaic cell by back connection with a cover material, selected made of glass or composite material. A method according to claim 7, characterized in that the seal by heating the cell to a temperature above the softening temperature of the transparent, electrically insulating material ( 1 ) and the covering material. Use of photovoltaic cells according to a of claims 1 to 4 as solar cells, solar panels or photo-electrochemical converters that are both outdoor and in Buildings can be used.