Towards Sinter-free Printing of Photovoltaic Cell Interconnects

Lead Research Organisation: University of Liverpool
Department Name: Centre for Materials and Structures


Metal thin films are used in a wide variety of technologies, such as solar cells and printed circuit boards for electronics. Inkjet printing has emerged as a practical and low-cost route for manufacturing electrical contacts in these applications. However existing manufacturing technologies use inks that often require a final heat treatment to consolidate or 'sinter' the film. If this last step can be eliminated, by depositing fully dense films, then the inkjet manufacturing process could be applied to temperature sensitive substrates like plastics or vulnerable semiconductor materials.

The purpose of this project is to develop 'sinter-free' inkjet manufacturing processes, by taking ink precursors developed for other thin film processes, and exploiting them to use the significant benefits of inkjet process technology e.g. the direct writing of interconnects or wires. If successful, the project will represent a step-change in the manufacturing methods for this type of film.

Planned Impact

Inkjet printing has become a rapidly expanding commercial technology. The total inkjet print market in 2009 was $26.8 billion, 58.2% higher than in 2005. Market forecaster's Pira expect continuing growth, averaging 10.3% CAGR from 2010-15 and anticipates that the market will be worth $46.5billion. In the context of photovoltaics, inkjet printing is used to fabricate contacts and bus bars on the surface of solar cells. Ink jetting has several advantages, including the ability to print narrow features with high resolution. This minimises shadowing and increases the cell efficiency. Direct-write printing also reduces the number of process steps, speeds set-up time, eliminates waste, reduces cost through automation, and enables non-contact printing for thin, sensitive substrates. Thin film PV is currently under 20% of the total global PV production, which is dominated by crystalline silicon. However, thin film PV output which is now dominated by cadmium telluride and is increasing more rapidly than crystalline silicon. The UK has a very strong PV supply chain industry with companies such as Crystalox producing multi-crystalline silicon wafers, Dupont who are a major supplier of conductive pastes and Pilkington NSG which is now the world's largest supplier of transparent conducting oxides (TCOs) for thin film PV.

Inkjet is a significant process technology in printed electronics and includes applications from printed silver interconnects between panels or devices to completely printed computing chips. Printed electronics is moving towards reduced fabrication costs a wide range of devices including displays, sensors, batteries, RFID chips, etc. Inkjet is a mask-less technology that is presently an established tool in plastic electronics R&D and is ideally suited to make certain devices. The primary opportunity is for conductive inks -especially silver inks-but semiconducting and dielectric inks will also be an important part going forward.

The project will impact upon a range of industrial sectors including inkjet printing and processing equipment (Xaar, Renishaw and OpTek Systems); printing inks and precursors (Dupont and SAFC Hitech); end users in photovoltaics (Optic Technium and NSG).


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Description The original grant contained 4 objectives these have been fully met in this work.
1) we have developed very novel injet ink formulations based on ROM's
2) We have successfully printed these and measured their electrical performance
3) We have demonstrated their use proving their environmental efficacy
4) We have demonstrated their use in photovoltaics
Exploitation Route We are currently seeking IP protection for our work and are working with several companies on exploitation of the results
Sectors Aerospace, Defence and Marine,Chemicals,Creative Economy,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

Description We are currently exploiting the research in several areas including further grant awards from EPSRC including EP/N017773/1, EP/L01534X/1, EP/P027318/1 and EP/N013778/1 Several other funded research projects include commercial research for companies that can not be divulged here because of confidentiality agreements.
Sector Chemicals,Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic

Description Integrated anode-less PEM fuel cells (iaPEM-FC) - beyond hydrogen
Amount £498,835 (GBP)
Funding ID EP/N013778/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2016 
End 12/2019
Description Reactive Metal Jet Fusion Printing
Amount £958,074 (GBP)
Funding ID EP/P027318/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 05/2017 
End 05/2020
Description EpiValence manufacturing of ROM inks 
Organisation EpiValence Limited
Country United Kingdom 
Sector Private 
PI Contribution EpiValence Ltd are a UK manufacturer and SME who develop specialist chemicals mainly for the surface coating industry. The work that the research team completed on the use of ROM inks has developed into a research partnership developing specialist inks for the additive manufacturing industry. EpiValence are project partners on a new EPSRC award investigating reactive inks in metal AM
Collaborator Contribution EpiValence supplied materials and know how to the project allowing us to set the reactivity and the fluidic properties of the inks
Impact There are no specific outputs yet as the work has just started. We hope to be able to reveal some new development soon bu they are subject to IPR restrictions
Start Year 2017
Description FEI UK Ltd 
Organisation FEI company
Department FEI United Kingdom
Country United Kingdom 
Sector Private 
PI Contribution This partnership has just started
Collaborator Contribution This partnership has just started
Impact None as yet
Start Year 2017
Description Ford Motor Co 
Organisation Ford Motor Company
Country United States 
Sector Private 
PI Contribution This is a brand new partnership and as such no contributions have been made by either side at the moment
Collaborator Contribution This is a brand new partnership and as such no contributions have been made by either side at the moment
Impact None at present
Start Year 2017
Description LPW Technology Ltd (UK) 
Organisation LPW Technology Ltd
Country United Kingdom 
Sector Private 
PI Contribution We have developed understanding and metallurgical knowledge of the powders and their usage for LPW. This knowledge has recently been extended to the interaction of powders with ROM inks. We have trained a range of staff from COO level to technician at maseted and PhD level
Collaborator Contribution LPW have developed and supplied a range of specialist metallic powders
Impact PhD training Donal Lynch
Start Year 2010
Description ScottAM 
Organisation Scott-AM Ltd
Country United Kingdom 
Sector Private 
PI Contribution We have been working with Scott AM on the development of Reactive Inkjet Printing. Out contribution so far has been the transfer of knowledge to the company
Collaborator Contribution Scott AM has developed an understanding of the AM process using reactive inkjets and is currently looking to actively exploit the technique.
Impact Transfer of knowledge partnership building
Start Year 2017
Description The Technology Partnership Plc (TTP) 
Organisation Technology Partnership Plc
Country United Kingdom 
Sector Academic/University 
PI Contribution TTP develops and supplied inkjet heads that can jet particularly viscous liquids which are idea for out ROM inks and ROM ink suspensions. WE have introduced TTP to our technology allowing them to develop bespoke solutions for our research
Collaborator Contribution TTP have developed bespoke solutions for the jetting of heavily loaded fluids
Impact Ink jet heads which can jet heavily loaded ROM fluids
Start Year 2016
Description A method of 3D printing comprises: providing a layer of a powder bed; jetting a functional binder onto selected parts of said layer, wherein said binder infiltrates into pores in the powder bed and locally fuses particles of the powder bed in situ; sequentially repeating said steps of applying a layer of powder on top and selectively jetting functional binder, multiple times, to provide a powder bed bonded at selected locations by printed functional binder; and taking the resultant bound 3D structure out of the powder bed. 
IP Reference WO2019025801 
Protection Patent application published
Year Protection Granted 2019
Licensed No
Impact ADDITIVE MANUFACTURING COMPONENTS AND METHODS The research team and the UoL Research Partnersips and Innovation team are currently discussing various licencing and spin-out opportunities with leading international companies.
Description Women in Science and Engineering event 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Debate on Additive Manufacturing research discussing the research carried out in universities in the UK and worldwide. The impact that this research has on society. This was to better inform the public in what AM is and what its impacts are on society.
Year(s) Of Engagement Activity 2017