WO2010128459A1

WO2010128459A1 - Method of manufacturing a photovoltaic device and device thus obtained

Info

Publication number: WO2010128459A1
Application number: PCT/IB2010/051964
Authority: WO
Inventors: Fabio Renato Cappelli; Stefano Segato; Antonio Maroscia
Original assignee: Fabio Renato Cappelli; Stefano Segato; Antonio Maroscia
Priority date: 2009-05-05
Filing date: 2010-05-05
Publication date: 2010-11-11
Also published as: SM200900034B; SM200900034A; WO2010128459A8

Abstract

A method of making a photovoltaic device comprises the application of a multilayer paint, by providing: a support (T) with an outer surface (E), a first base layer (1) of an electronically, chemically and mechanically inert material deposited onto the surface (E), a first connector (6), a second electrode layer (2) with a predetermined electronic potential, a third layer (3) of an optoelectronically active material, a fourth counter-electrode layer (4) having an electronic potential different from that of the second layer (2), a second connector (7), a fifth protective layer (5) of an optically transparent material. The materials of the layers (1-5) are initially in the liquid or pasty state. The materials of at least two contiguous layers (2, 3; 3, 4) selected among the central layers (2, 3, 4) are premixed (i) to form a substantially homogeneous mixture (M) to be evenly applied to the first base layer (1) and undergo a controlled layering step (m).

Description

METHOD OF MANUFACTURING A PHOTOVOLTAIC DEVICE AND DEVICE THUS OBTAINED

Field of the invention

The present invention finds application in the field of renewable energies and particularly relates to a multilayer photovoltaic paint capable of controlled layering, which is susceptible of absorbing solar radiation or anyway the photons impinging thereon, and convert it into electric energy.

The invention also relates to a method of applying said paint to make a photovoltaic device, as well as a photovoltaic device obtained from said paint using said method.

Background art

Patent US-B-6,013,871 , issued to Lawrence, discloses a photovoltaic device composed of multiple layers of paint or metal oxides, immersed in a polymer matrix and coated with a layer of clear material to allow the passage of light.

This known device comprises most of the features as set out in the preamble of claim 1.

A peculiar feature of this prior art paint is that the layer deposition process is carried out using materials in a liquid or pasty state, which allows the use of highly simple deposition techniques, i.e. spray, paintbrush, palette-knife painting techniques or the like.

Advantageously, the layers have very small thicknesses, i.e. from a few nm to a few μm, which dramatically reduces the cost of the photovoltaic panels that can be obtained from said paint and allows them to fit any shape. A further aspect of the above mentioned photovoltaic paint is that none of the layers contains silicon oxides, which obviates the need for a supply of these materials.

The process for application of said multilayer paint includes the steps of depositing the layer of base material onto the outer surface of the support, to form an anchoring surface, and later successively depositing the remaining layers thereby defining a unitary wafer.

This process allows photovoltaic devices to be formed on surfaces of any type and size, with low costs and in an easy manner.

While this known method provides considerable advantages and perfectly fulfill its intended purpose, it still requires the deposition of a large number of layers of different materials, each having a special task. This involves increase of deposition times and costs, thereby increasing times and costs for making the device.

In order to reduce the times and costs of industrial-scale production of photovoltaic devices, it would be helpful to simplify and accelerated the method of deposition of the various layers of paint, by reducing the number of coats and hence the times and costs for making the device.

Particularly, fewer coats should be applied at later times, while maintaining the performances of the device so obtained substantially unchanged or reduced within acceptable limits.

Disclosure of the invention

These objects are fulfilled by a method that comprises the application of a multilayer photovoltaic paint of the invention, in which the materials of at least two adjacent layers selected among the second electrode layer, the third active layer and the fourth counter-electrode layer are preliminary mixed to form a homogeneous mixture, and in which the homogeneous and undifferentiated mixture is unitarily applied to said first base layer and later undergoes a precipitation, separation and controlled layering phase, to promote the formation of said two separate and differentiated adjacent layers.

Preferably, the homogeneous mixture is composed of the materials that form the second electrode layer, the third active layer and the fourth counter- electrode layer, which mixture, after application thereof to the base layer, undergoes precipitation, separation and controlled layering to promote the formation of these three differentiated adjacent layers.

This method affords faster simultaneous application of two or three layers, without requiring any further coat application, as well as good-quality layering and relatively low costs.

A photovoltaic electric energy generating device is manufactured by carrying out the above method steps to form the central layers, and to apply the electric connectors, also in the form of a liquid or pasty material.

Brief description of the figures

Further features and advantages of the invention will be more apparent upon reading of the description of one embodiment of the method of the invention, which is described by way of example and without limitation with the help of the annexed drawings, in which: FIG. 1 shows a cross sectional view of a photovoltaic device obtained with the method of the invention; FIG. 2 shows a block diagram of the method of making a photovoltaic apparatus as shown in FIG. 1 by application of the multilayer photovoltaic paint according to the invention;

FIG. 3 shows a diagrammatic view of a production line for implementing the method as depicted in the block diagram of FIG. 2;

FIG. 4 shows a diagram of the temperatures of certain components of the paint during applicants of the same.

Description of a preferred embodiment

Referring to FIG. 1 , a photovoltaic device of the invention is shown in a cross sectional view. The device, generally designated by numeral 100, may be formed on any movable or stationary support T having an outer surface E that may be oriented toward a light source S.

By way of non-limiting example, the support T may consist of a wall, a plate or a fabric of any material, having any planar, convex or 3D shape.

The device 100 essentially consists of a photovoltaic paint having multiple layers, each having a special task, applied to the outer surface E of the support T.

A first base layer 1 is provided in contact with the surface E, which is made of an electronically, chemically and mechanically inert material, has a very low surface roughness, and is from a few nm to a few μm thick, thereby defining a substantially smooth and homogeneous anchoring surface.

A series of layers 2, 3, 4 referred to as "intermediate" layers, i.e. interposed between upper and lower layers, is laid on the first layer.

Particularly, the second layer 2 is made of an electrically conductive material with a predetermined electronic potential, defining an electrode. For example, the material of the layer 2 will be selected to have a relatively high work function, from 4 eV to 6 eV, for effective hole collection.

A third layer 3 of an optoelectronically active material is laid on the layer 2, and is designed to convert photons from the light source S into electrons. The material/s that form the third layer 3 shall ensure as high light absorption as possible and efficient generation of electric charges, as well as transfer thereof towards the electrodes.

A fourth layer 4 of a second electrically conductive material is laid on the third active layer, which material has an electronic potential different from that of the layer 2, and shall have a low work function, e.g. from 3 eV to 4.5 eV, to facilitate negative charge connection and define a counter-electrode. Besides being a good conductor, the fourth layer 4 shall have the characteristic of being optically transparent in the spectral region of solar radiation.

The layers 2, 3 and 4 shall be briefly defined hereinafter as intermediate layers.

A fifth protective layer 5 of an optically transparent material is laid on the intermediate layers 2, 3 and 4, to define a protective sealing barrier against external agents and particularly oxygen.

Conveniently, electric charge extraction and current flow are allowed by connector elements, designated by numerals 6, 7 respectively, made of electrically conductive materials, and placed in contact with the electrode 2 and counter-electrode 4 layers.

As is known per se, the connectors 6, 7 extend through the protective layer 5 for connection by conventional cables to a network or an external user unit. A method of making a device 100 as described above may include the steps of: a) providing a movable and/or stationary support T having a surface E susceptible of being oriented toward the light source S; b) possibly providing a first base layer 1 of an electronically, chemically and mechanically inert material on the surface E; c) providing at least one first connector 6 made of an electrically conductive material; d) providing at least one second layer 2 of an electrically conductive material with a predetermined electronic potential defining an electrode; e) providing at least one third layer 3 made of an optoelectronically active material; f) providing at least one fourth layer 4 of a second electrically conductive material with an electronic potential different from that of the second layer 2 defining a counter-electrode; g) providing at least one second connector 7 made of an electrically conductive material in contact with the counter-electrode layer 4; h) possibly providing at least one fifth protective layer 5 of an optically transparent material to define a protective sealing barrier against external agents.

According to the invention, the materials of all the layers 1 , 2, 3, 4 and 5 paint layers are initially in a liquid or pasty state.

In a preferred embodiment, the connectors 6, 7 are also layers which are initially in a liquid or pasty state.

In the context, the term "adjacent or contiguous layers" is intended to define mutually contacting layers with no intermediate layer therebetween: this definition includes the pairs of layers 1-2, 2-3, 3-4, 4-5, but not the pairs of layers 1-3, 3-5 or 2-4.

According to the invention, at least two adjacent or contiguous layers selected from the layers 1 , 2, 3, 4, 5 undergo a preliminary mixing step i) to form a substantially homogeneous undifferentiated mixture M.

Preferably, said mixture M is obtained by premixing at least two of the intermediate layers 2, 3 and 4.

After such premixing step i), the mixture M is unitarily applied to the first base layer 1 and undergoes a controlled layering step j) to promote the formation of adjacent differentiated central layers 2, 3 and 4. For instance, the mixture M may be obtained by mixing the materials of the adjacent layers 2 and 3, or the adjacent layers 3 and 4, but not the layers 2 and 4 that are separated by the active layer 3.

It shall be noted that the percentages by weight or mass of the materials that form the mixture M are proportional to the thicknesses of the corresponding adjacent layers to be formed.

In a preferred embodiment, as shown in the drawings, the mixture M is composed of the materials that form the three layers 2, 3 and 4, and the controlled layering step j) has the purpose of differentiating and stabilizing these three central layers, as if they had been separately deposited.

In an alternative embodiment, not shown, a larger number of layers may be initially mixed, e.g. the three central layers and the first base layer, for later differentiation and controlled layering as mentioned above, without departure from the scope of the invention.

During the initial mixing step i), the mixture M of materials undergoes a pre- heating step j) and is maintained at a first controlled temperature Ti to prevent settling.

For this purpose, the mixture M is placed in a container 8 and subjected to pre-hearting j), e.g. through Joule effect, using a generator 9 of electromagnetic waves in the radio-frequency range.

Furthermore, the mixture M in the container 8, which is preferably hermetically sealed and filled with inert gas, e.g. nitrogen, undergoes a continuous stirring step k), e.g. by a conventional rotating stirrer 10.

Thus, a controlled-atmosphere turbulent regime is induced in the mixture, to make it as homogeneous as possible and reduce oxidation.

Suitably, the pre-heating temperature Ti may be comprised in a range from 40° to 250°C, depending on the materials that form the layers 2, 3 and 4 and is maintained at such substantially constant value with a predetermined tolerance ΔTi, e.g. comprised in a range from 0,2°C to 5°C, preferably about 0,5°C, for optimized homogenization of the mixture M.

The pre-heated and homogenized mixture M is extracted from the container 8 and conveyed through a pump 11 , e.g. of peristaltic type, to a distribution head 12 having a set of nozzles 13 of the ink-jet type or the like.

The head 12 performs a step I) of substantially even spreading of the mixture M on the base layer 1 , by a micro-bubble jet at relatively high velocity V. The relatively high velocity of the jet is substantially constant and is selected for the mixture flow to be maintained in a substantially laminar condition, free of any transverse velocity component and/or convective motion, for maximized homogeneity of the undifferentiated deposited layer. Furthermore, the head 12 is maintained at a second operating temperature T₂ substantially close to said first pre-heating temperature Ti, e.g. using a microwave oven 13 capable of very accurate control of heat supplied to the mixture M. Such temperature T₂ is constant and preferably falls in a range from 45 to 220⁰C, with a tolerance ΔT₂ from 0,1 to 1 ,0⁰C.

Preferably, the jet is formed by a plurality of nozzles 14 situated at a predetermined small distance H from the base layer 1 , to reduce oxidation of said micro-bubbles.

According to the invention, the step of controlled layering m) of the substantially homogeneous undifferentiated layer is carried out through a series of successive cooling steps ΔQj_.

Such cooling steps ΔQj may occur seamlessly or in a stepwise manner and are as many as the materials that form the mixture M. Furthermore, such cooling steps ΔQj have a predetermined duration Δti, Δt₂, Δt₃ for each component of the homogeneous undifferentiated mixture M to be cooled to successive temperatures T_Oi , T₀₂, T₀₃ lower than said second temperature T₂.

Preferably, each temperature differs from the previous one by a range from 0,1 °C to 2,0°C, preferably by about 0,5°C.

Such cooling steps are carried out by heat removal ΔQi, ΔQ₂, ΔQ₃ through convection/conduction and/or contact with the layer of homogeneous mixture M.

A suitable deposition step m) is further provided in which at least one first strip 6 of electrically conductive material is deposited on the first base layer 1 , in contact with the second electrode layer 2, to define a first electric connector, and at least one second strip 7 of electrically conductive material is deposited on the fourth electrode layer 4 to define the second electric connector.

Finally, a curing step n) is provided in which both the layers and the connectors are cured by UV radiation, to stabilize the whole device.

The method and device of this invention are susceptible to a number of changes or variants, within the inventive concept disclosed in the annexed claims. All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departure from the scope of the invention.

While the method and device have been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Claims

1. A method of making a photovoltaic device comprising the application of a multilayer controlled-layering paint, through the following steps: a) providing a support (T) having an outer surface (E) susceptible of being oriented toward a light source (S); b) optionally providing at least one first base layer (1) of an electronically, chemically and mechanically inert material on the surface (E); c) providing at least one first connector (6) made of an electrically conductive material; d) providing at least one second layer (2) of an electrically conductive material with a predetermined electronic potential defining an electrode; e) providing at least one third layer (3) made of an optoelectronically active material; f) providing at least one fourth layer (4) of a second electrically conductive material with an electronic potential different from that of the second layer (2) defining a counter-electrode; g) providing at least one second connector (7) made of an electrically conductive material in contact with the counter-electrode layer (4); h) optionally providing at least one fifth protective layer (5) of an optically transparent material to define a protective sealing barrier against external agents; wherein the materials of said layers (1 , 2, 3, 4, 5) are initially in the liquid or pasty state, and wherein the materials of at least two adjacent or contiguous intermediate layers (1-2, 2-3, 3-4, 4-5) undergo preliminary mixing (i) to form a substantially homogeneous mixture (M), said mixture (M) being evenly applied to said surface (E) and undergoing a controlled layering step (m) to promote the formation of said at least two separate and differentiated contiguous layers (2-3, 3-4).

2. Method as claimed in claim 1 , wherein the materials of said mixture (M) consist of the materials of at least two adjacent layers selected from the intermediate layers (2, 3, 4), said mixture being evenly applied to said first base layer (1) and undergoing a controlled layering step (m) to provide the formation of said at least two differentiated contiguous layers (2-3; 3-4).

3. Method as claimed in claim 1 or 2, wherein the weight or mass of the materials forming said mixture (M) are proportional to the thicknesses of the corresponding adjacent layers to be formed.

4. Method as claimed in claim 1 or 2, wherein said preliminary mixing step (i) is carried out by pre-heating (j) said mixture and maintaining it at a first controlled temperature to prevent settling thereof.

5. Method as claimed in claim 4, wherein said preliminary heating (j) is obtained through Joule effect, e.g. by application of radio-frequency electromagnetic waves.

6. Method as claimed in claim 4, wherein during said pre-heating step G), said mixture undergoes a continuous stirring step (k) in a substantially turbulent flow condition, to maintain substantial homogeneity of said mixture.

7. Method as claimed in claim 4, wherein said first pre-heating G) temperature (T1) is maintained at a substantially constant value within a predetermined tolerance.

8. Method as claimed in claim 7, wherein said first substantially constant temperature (T1) is from 40°C to 250⁰C depending on the constituent materials.

9. Method as claimed in claim 7, wherein said predetermined tolerance (ΔT1) is from 0,2⁰C to 20⁰C and preferably about 0,5⁰C.

10. Method as claimed in claim 1 or 2, wherein said step of even application of said mixture (M) is carried out by undifferentiated spreading (I) using jet devices (12).

11. Method as claimed in claim 10, wherein said undifferentiated spreading step (I) is carried out by a flow of micro-bubbles at relatively high and substantially constant velocity (V) and at a second operating temperature (T2) close to said first pre-heating temperature (T1).

12. Method as claimed in claim 11 , wherein said relatively high velocity is selected for said micro-bubble flow to be maintained at a substantially laminar flow rate, with no substantially transverse velocity component or convective motion.

13. Method as claimed in claim 12, wherein during deposition of said jet of mixture, said second temperature (T2) is substantially constant and falls in a range from 54°C to 220°C with a tolerance (ΔT2) from 0,1 to 1 ,0⁰C.

14. Method as claimed in claim 12, wherein said jet is formed by a plurality of nozzles (13) situated at a predetermined small distance (H) from said base layer (1), to reduce oxidation of said micro-bubbles.

15. Method as claimed in claim 13, wherein said controlled layering (m) of said substantially homogeneous undifferentiated layer of mixture (M) is carried out through a series of cooling steps (ΔQj).

16. Method as claimed in claim 15, wherein said cooling steps (ΔQj) occur in a stepwise manner and are as many as the materials that form said mixture.

17. Method as claimed in claim 16, wherein said cooling steps (ΔQ,) have a predetermined duration (Δt,), for each component of said homogeneous undifferentiated mixture to be cooled to successive temperatures lower than said second temperature.

18. Method as claimed in claim 17, wherein each temperature differs from the previous one by a range from 0,1⁰C to 20,0⁰C preferably by about 0,5⁰C.

19. Method as claimed in claim 18, wherein said cooling steps are carried out by heat removal (ΔQ,) through convection and/or conduction and/or contact with said layer of homogeneous mixture.

20. Method as claimed in claim 1 , wherein said first connector (6) is obtained by depositing at least one first strip of electrically conductive material on said first base layer (1) so that it is in contact with said second layer (2).

21. Method as claimed in claim 19, wherein said second connector (7) is obtained by deposition of at least one second strip of electrically conductive material on said fourth counter-electrode layer (4).

22. Method as claimed in one or more of the preceding claims, wherein the materials forming at least some of said layers (1-5) and said connectors (6, 7) have a are polymeric basis and undergo a stabilization and/or curing step (n) by UV radiation.

23. A photovoltaic electric current generating device (100) comprising a multilayer photovoltaic paint obtainable by the method as claimed in one or more of the preceding claims.