Spray on Solar PV

New Energy Technologies Inc. have been promoting a new spray-on, see through solar PV coating which can be applied to glass windows.  Earlier this year they were indicating that around 20 new patent filings have been submitted for their proprietary SolarWindow™ technology.  Last year I reported on one of the early patent filings and the article can be viewed here.  Dr Xiaomei Jiang has been leading this effort with New Energy Technologies under a Sponsored Research Agreement at the University of South Florida (USF).

Two more patent applications have emerged this month from Dr Jiang at USF and they continue to reveal further details of the spray on techniques and solar PV architecture.

US20130255757: ORGANIC PHOTOVOLTAIC ARRAY AND METHOD OF MANUFACTURE

Publication date: 03/10/2013

Inventor(s): JIANG XIAOMEI JANE [US]; LEWIS JASON ERIK [US]

Abstract

The fabrication and characterization of large scale inverted organic solar array fabricated using all-spray process is disclosed, consisting of four layers; ITO-Cs2CO3-(P3HT:PCBM)-modified PEDPT:PSS, on a substrate. With PEDPT:PSS as the anode, the encapsulated solar array shows more than 30% transmission in the visible to near IR range. Optimization by thermal annealing was performed based on single-cell or multiple-cell arrays. Solar illumination has been demonstrated to improve solar array efficiency up to 250% with device efficiency of 1.80% under AM1.5 irradiance. The performance enhancement under illumination occurs only with sprayed devices, indicating device enhancement under sunlight, which is beneficial for solar energy applications. The semi-transparent property of the solar module allows for applications on windows and windshields, indoor applications, and soft fabric substances such as tents, military back-packs or combat uniforms, providing a highly portable renewable power supply for deployed military forces.

US20130263916: ALL SPRAY SEE-THROUGH ORGANIC SOLAR ARRAY WITH ENCAPSULATION

Publication date: 10/10/2013

Inventor(s): LEWIS JASON ERIC [US]; JIANG XIAOMEI JANE [US]

Abstract

An inverted organic solar photovoltaic cell is described that may be fabricated onto rigid or flexible substrates using spray-on technology to apply the various layers of the cell. Indium tin oxide with a thin layer of cesium carbonate functions as the cathode for the novel inverted cells. An active layer of poly-3(hexylthiophene) and [6,6]-phenyl C61-butyric acid methylester having a thickness around 200 nm to 600 nm facilitates a high level of light transmittal through the cell. A modified PEDOT:PSS, made by doping a conductive polymer with dimethylsulfoxide (DMSO), functions as the anode. A method of forming the inverted organic solar photovoltaic cell is also described using gas-propelled spraying to achieve thin layers. After the layers are formed, the cell is sealed using a vacuum and temperature-based annealing and encapsulation with UV-cure epoxy.

Phil’s Comments:

These applications are going through the patent office examination process so it is difficult to comment on the claims until we know what will actually be allowed.  The claims do make reference to spraying and the second application indicates that nitrogen is used as a propellant.

The device is an inverted solar cell design and may be fabricated onto both rigid and flexible substrates. Exemplary substrates include cloth, glass, and plastic. For example, the substrate may be a low alkaline earth boro-aluminosilicate glass.

Two figures from the second application are shown below:

FIG. 1 is a diagram that depicts the modified PEDOT:PSS as it is sprayed onto the substrate through a stainless steel shadow mask with an airbrush. Nitrogen is used as the carrier gas at a pressure of 20 psi.

FIG. 13 is a diagram showing the cross sectional view of the device architecture of an inverted solar array showing series connection

Figure 1 Capture2

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Printed Electronics using Graphene based Inks

When I spotted a recent granted patent with the title Printed Electronics, it was an obvious candidate for a Phil’s Patent Pick.  US8278757 was published on 2nd October 2012 and jointly assigned to Vorbeck Materials Corp. and Univ. of Princeton.  It was originally filed on 9th January 2009 and has a priority date of 5th February 2008.

The patent has quite broad claims and describes printed electronics devices made using a conductive ink comprising functionalized graphene sheets and a binder.  I don’t always reproduce the claims but in this case they are fairly simple to follow:

1. A printed electronic device, comprising a substrate comprising at least one surface, wherein a layer of an electrically conductive ink has been applied to a portion of the surface, and wherein the ink comprises functionalized graphene sheets and at least one binder.

2. The device of claim 1, wherein the substrate comprises paper and/or cardboard.

3. The device of claim 1, wherein the substrate comprises at least one polyolefin.

4. The device of claim 1, wherein the substrate comprises at least one polyimide.

5. The device of claim 1, wherein the ink further comprises at least one dispersant.

6. The device of claim 1, wherein the binder is a polymeric binder.

7. The device of claim 6, wherein the binder is one or more of poly(ethylene oxide), poly(propylene oxide), and ethylene oxide/propylene oxide copolymers.

8. The device of claim 1, wherein the ink further comprises at least one metal component.

9. The device of claim 8, wherein the metal is silver and/or copper.

10. The device of claim 1, wherein the ink further comprises at least one electrically conductive polymer.

11. The device of claim 1, wherein the ink further comprises at least one carbonaceous material other than the functionalized graphene sheets.

12. The device of claim 1, wherein the functionalized graphene sheets have a surface area of from about 300 to about 2630 m²/g.

13. The device of claim 1, wherein the functionalized graphene sheets have a surface area of from about 400 to about 2400 m²/g.

14. The device of claim 1, wherein the functionalized graphene sheets have a carbon to oxygen ratio of about 60:40 to 20:1.

15. The device of claim 1, further comprising one or more components selected from the group consisting of processors, memory chips, batteries, resistors, diodes, capacitors, and transistors.

16. The device of claim 1 in the form of an integrated circuit.

17. The device of claim 1 in the form of a printed circuit board.

18. The device of claim 1 in the form of a light-emitting diode display.

19. The device of claim 1 in the form of a radiofrequency identification device and/or a radiofrequency device antenna.

20. The radiofrequency identification device and/or radiofrequency device antenna of claim 19 in the form of a radiofrequency identification device and/or antenna for use with ultra-high frequencies.

21. A method for forming a printed electronic device, comprising the step of applying an electrically conductive ink to a substrate, wherein the ink comprises functionalized graphene sheets and at least one binder.

22. The method of claim 21, wherein the substrate is selected from one or more of paper, cardboard, polyolefin, and polyimide.

23. The method of claim 21, wherein the electrically conductive ink further comprises a carrier.

24. The method of claim 21, wherein the electrically conductive ink further comprises a dispersant.

25. The method of claim 21, wherein the functionalized graphene sheets have a surface area of from about 300 to about 2630 m²/g.

Phil’s Comments

It is worth looking at the examples in the patent.  The printing methods and samples generated for testing are pretty crude and suggest that only simple circuits have been generated such as RFID antennas.  The type of ink suggests that printing processes will be of the gravure or flexo type rather than ink-jet.  However, the wording of the allowed claims suggests that just about any printed electronic device containing a layer that includes graphene sheets with a functional group in a binder would infringe this patent.  The majority of the claims are all about the device and not the material.  The last five claims are about the method.  Vorbeck sell the graphene based inks and with this patent they will require anyone using the inks to enter into some form of agreement with them to make the devices.  It will be interesting to see how this works in practice and whether the patent will stand the test of time.

Can you really spray on Solar cells?

Back in January 2010 New Energy Technologies unveiled a patent pending process for “spraying” solar panels and their related components onto glass.  The spray concept seemed to catch the publics imagination and of course the idea that you could simply spray from a can onto glass and have a functioning solar window does indeed seem a fantastic breakthrough.  The reality is somewhat different and while the research does indeed show that functional organic layers can be spray coated onto a substrate this is but one step of a multi-phase process to create a fully functional solar panel.

Although the patent applications had been filed a considerable period has to elapse before they become published and available in the public domain.  Earlier this month one of the US patent applications was published and so it is possible to delve a bit deeper into the technology that is being developed.  The research is based on the work of Professor Xiaomei Jiang in the Nanostructure Optoelectronics Lab at the University of South Florida.  New Energy Technologies Inc. are in the process of developing their SolarWindow™ product using this technology.  More recently they have entered into a cooperative Research and Development agreement with the US Department of Energy’s National Renewable Energy Lab. to advance development of SolarWindow™.

The patent application is US20120156825 and summary details are shown below:

Title: Transparent Contacts Organic Solar Panel by Spray

Inventors: Jason Lewis, Jian Zhang, Xiaomei Jiang

Assignee: University of South Florida

Abstract: A method of fabricating organic solar panels with transparent contacts. The method uses a layer-by-layer spray technique to create the anode layer. The method includes placing the substrate on a flat magnet, aligning a magnetic shadow mask over the substrate, applying photoresist to the substrate using spray photolithography, etching the substrate, cleaning the substrate, spin coating a tuning layer on substrate, spin coating an active layer of P3HT/PCBM on the substrate, spray coating the substrate with a modified PEDOT solution, and annealing the substrate.

Claims: The first six claims are worth noting:

1. A method of fabricating organic solar panels with transparent contacts, comprising: applying photoresist to a substrate by spray photolithography; spin coating a tuning layer on the substrate; spin coating an active layer coating on the substrate; spray coating the substrate with a modified PEDOT solution; and annealing the substrate.

2. The method of claim 1, wherein the substrate is an ITO glass substrate.

3. The method of claim 1, wherein the substrate is plastic.

4. The method of claim 1, wherein the substrate is cloth.

5. The method of claim 1, wherein the tuning layer is Cs2CO3.

6. The method of claim 1, wherein in the active layer coating is P3HT/PCBM.

There are an additional 17 claims which give further details of the method.

Phil’s comments:  As you can see the concept of simply spraying a solar cell onto glass is a long way from reality.  However, this patent application does explain the technical approach quite well and indicates that the various layers including the contacts are all transparent so that the final result is a solar cell on glass that will still resemble a window.

Printing Electronic Features on Uneven Surfaces

A recently granted patent caught my eye because it made reference to a method of ink jet printing conductive inks onto non-uniform surfaces.  The patent was granted to the Cabot Corportion who currently provide a number of inkjet formulations for printed electronics applications.  This patent indicates that they have also been working on a system of direct printing which can compensate for the uneven surface of a substrate.

Patent details:

US8167393: Printable Electronic Features On Non Uniform Substrate And Processes For Making Same

Filing Information:
Inventor(s):    Karel Vanheusden, Chuck Edwards
Assignee(s):    Cabot Corporation

Filing date    13/01/2006
Issue date    01/05/2012
Prior Publication Data:     US20060158470 – 20/07/2006

Abstract:  A system and process for compensating for non-uniform surfaces of a substrate when direct printing traces is provided. The system and process provided herein measures the surface of a substrate and can determine whether the surface is substantially flat, rises or falls, or whether a mesa or valley is encountered. Depending on the surface feature (i.e., mesa, valley, falling or rising surface), the direct printing system can change the frequency of the printing timing signal, advance or retard the print timing signal, advance or retard the print data, or make repeated passes over certain areas. In addition, the process disclosed herein can determine whether two, three or all of the aforementioned steps for compensating for non-uniform substrates should be combined to most effectively and efficiently print on the non-uniform surface of the substrate as intended.

The invention seems to be primarily for printing on surfaces which have already received some printed circuit tracks or components and need to have additional conductive tracks to complete the device.  However, the text describes the situation where you might want to print directly onto an uneven or flexible substrate.  With a conventional printhead the drops will become more spaced out if the distance between the head and the substrate increases due to a downward slope.  If there was an upward slope then the drops will land closer together.

Various ways are described to overcome this problem and enable a uniform print density and line thickness to be achieved.  The distance between the printhead and the surface can be continually monitored with a laser interferometer so that the surface topography is mapped and used to control the drop delivery.

The patent has a huge number of document references and also contains a useful review of the background art associated with more traditional printing processes such as photolithography and screen printing.

This does seem to be a serious attempt at reducing the impact of an uneven surface on the reliability and quality of printed conductive tracks and I would be interested to hear from anyone who has looked at other ways of addressing this problem.

Printed electronics, tattoos and artificial skin

I came across a recent patent application from Nokia describing a haptic communication method in which labels or tattoos on the skin can be made to vibrate when triggered by a magnetic field.  In one example the magnetic field could be initiated by a mobile phone and the user could be alerted to incoming phone calls via the sensations induced on the users skin.

The patent application was published on 15th March 2012 as US20120062371

What is claimed is:
1. An apparatus comprising:
a material attachable to skin, the material capable of detecting a magnetic field and transferring a perceivable stimulus to the skin, wherein the perceivable stimulus relates to the magnetic field.
2. An apparatus according to claim 1, wherein the material comprises at least one of a visible image, invisible image, invisible tattoo, visible tattoo, visible marking, invisible marking, visible marker, visible sign, invisible sign, visible label, invisible label, visible symbol, invisible symbol, visible badge and invisible badge.
3. An apparatus according to claim 1, wherein the perceivable stimulus comprises vibration.

Several other claims go on to describe the material in more detail and indicate that it could comprise a ferromagnetic powder.

At about the same time The University of Cambridge were publishing in the Advanced Materials journal ( Vol 24, No. 12 pp. 1558-1565) an article on the progress made by researchers in the Cavendish Laboratory towards better flexible printed electronics materials.  The work was recently highlighted in the Research Features page and applications mentioned include artificial skin and interactive playing cards.  Many of these applications are a long way off yet but the groundwork to make them possible is progressing at a rapid rate.  The new circuits developed by Drs Kronemeijer and Gili exhibited the fastest operation published to date (a few hundred KHz) using a new class of ambipolar organic materials and reduced the power supply requirements by approximately one order of magnitude so that they can already be operated using a standard 9V battery.

If anyone would like to know more about the patent applications that are emerging in this highly competitive field then please contact me at IPScope (phil.coldrick@ipscope.co.uk).

Recent Patent may be concern for Printed Semiconductor Manufacturers

When looking through granted patents in any technical field it is always a concern if one turns up with broad claims that might impact a wide range of products or manufacturing processes.  Recently I came across one in the printed electronics field which might just be in that category.  Read on to see what it is all about.

US7982296 was granted on 19 July 2011 to the University of Illinois and has the title “Methods and Devices for Fabricating and Assembling Printable Semiconductor Elements”.  The abstract caught my eye because it was referring to flexible devices made on substances comprising polymeric materials and also to stretchable structures.

The invention provides methods and devices for fabricating printable semiconductor elements and assembling printable semiconductor elements onto substrate surfaces. Methods, devices and device components of the present invention are capable of generating a wide range of flexible electronic and optoelectronic devices and arrays of devices on substrates comprising polymeric materials. The present invention also provides stretchable semiconductor structures and stretchable electronic devices capable of good performance in stretched configurations.

I was able to trace the history of this application and found that the earliest documents associated with the filing were back in 2004 and that two patents were eventually granted, the earlier one related to the method for assembling the devices (US7622367) published on 24 Nov 2009 and this one just published being for the devices themselves.  The INPADOC patent family now consists of over 30 documents across several countries including Japan, Korea, Taiwan, and China.

The first claim is the broad one which I believe may give some concern to a number of manufacturers involved in printing inorganic semiconductors.  It reads:

1. An electrical device comprising: a first electrode; a second electrode; and a printable semiconductor element positioned in electrical contact with said first and second electrodes, said printable semiconductor element comprising a unitary inorganic semiconductor structure having at least one cross sectional dimension greater than or equal to about 500 nanometers.

The other 8 claims are all dependant claims and further refine claim 1.  A number of examples are included illustrating the range of devices in mind, some involve dry transfer printing, others solution printing.

The patent description is remarkably detailed with several pages of background references and 46 figures one of which is included below.

FIG. 26A illustrates the steps used to fabricate exemplary bendable thin film transistors devices of the present invention.

If you wish to explore the patent further it is best to review the pdf file which can be downloaded from the Espacenet website.

As always, please leave a comment if you want to discuss this further and visit my IPScope website for details of a range of Strategic IP Management services including patent searches.

Kovio Inc. patents: Printed Electronics Devices at lower cost

Background

The radio frequency identification (RFID) market is huge, already over £2 billion.  Within this market passive RFID is expected to be the prime candidate for printing but so far the main thrust has been the printing of the antennae.  Often silver inks are used but the price fluctuations of silver (currently very high) cause many companies to look for alternatives such as copper, aluminium and organic conductive polymers.  The expensive part of an RFID tag is the chip and there are not many companies who have tried printing the chips.  Kovio Inc. was the first using nanosilicon on a variety of substrates.

The real advantage of printed RFID is the potential to produce tags and labels cheaply, perhaps even being able to print them directly as is done with barcodes today.  Applications like library tags, that currently use high cost silicon memory chips, tend to use HF rather than UHF and I believe this is where the potential for printed RFID is to be found.

Kovio Patents

Kovio Inc. were recently granted a third patent in a series which all relate to methods for making devices such as RFID tags at lower cost.  The key phrase from their abstract is:

The present invention advantageously provides semiconducting thin film structures having qualities suitable for use in electronics applications, such as display devices or RFID tags, while enabling high-throughput printing processes that form such thin films in seconds or minutes, rather than hours or days as with conventional photolithographic processes.

Their recent series of patents are summarized in the table below:

The most recent patent can be viewed here and has 67 method claims, the earlier patents relate to the materials and the thin film structure.  The 7553545 patent is also interesting in that it details the linewidths and gaps that can be printed.