Lithographically Printed Voltaic CellsLithographically Printed Voltaic Cells

Sustainability and printed electronicsSustainability and printed electronics

�� D. Southee, P.S.A. Evans, D. Harrison & D. Southee, P.S.A. Evans, D. Harrison & G.I. HayG.I. Hay

�� Cleaner Electronics Research GroupCleaner Electronics Research Group�� School of Engineering and DesignSchool of Engineering and Design

�� Brunel University Brunel University

Sustainability Sustainability

�� Sustainability Sustainability -- ““meeting the NEEDS of today meeting the NEEDS of today

without compromising the ability of future without compromising the ability of future generations to meet their needsgenerations to meet their needs””

�� (from the Brundtland Report)(from the Brundtland Report)�� Example of Intergenerational EquityExample of Intergenerational Equity

MaslowMaslow’’s Hierarchy of Needss Hierarchy of Needs

�� Self actualisation (realising oneSelf actualisation (realising one’’s full potential)s full potential)�� Aesthetic NeedsAesthetic Needs�� Cognitive NeedsCognitive Needs�� Esteem NeedsEsteem Needs�� Love and Belongingness (Receiving and giving love and Love and Belongingness (Receiving and giving love and

affection)affection)�� Safety NeedsSafety Needs�� Physiological Needs (food, water, etc)Physiological Needs (food, water, etc)

Printed Electronics TodayPrinted Electronics Today

�� An enabling technology that is starting to help An enabling technology that is starting to help to meet some of these human needsto meet some of these human needs

�� But is it more But is it more ““sustainablesustainable”” than the than the

conventional technology it replaces?conventional technology it replaces?

Study on environmental impact of PCB Study on environmental impact of PCB replacement by replacement by ““printedprinted””

circuit circuit

�� Environmental Impact Evaluation of Additive Circuit Environmental Impact Evaluation of Additive Circuit Fabrication Processes Fabrication Processes Ramsey, Harrison Ramsey, Harrison

•• Conclusions:Conclusions:

•• Reduction of the discrete processes necessary Reduction of the discrete processes necessary during manufacture and elimination of the wet during manufacture and elimination of the wet chemical etching, plating and cleaning phases.chemical etching, plating and cleaning phases.

•• A reduction by an order of magnitude of the cost of A reduction by an order of magnitude of the cost of disposal of hazardous waste generated.disposal of hazardous waste generated.

••

A reduction in the volume of raw material which has A reduction in the volume of raw material which has to be processed to extract the metal for the to be processed to extract the metal for the conducting elements.conducting elements.

•• A reduction in the time per unit for manufacture A reduction in the time per unit for manufacture (reduced energy overhead).(reduced energy overhead).

�� These characteristics indicate the Conductive These characteristics indicate the Conductive Lithographic process is likely to be more Lithographic process is likely to be more environmentally benign for PCB production environmentally benign for PCB production than conventional PCB manufacture. than conventional PCB manufacture.

In the longer term, is there enough In the longer term, is there enough material, and is there enough energy to material, and is there enough energy to

sustain the processes?sustain the processes?

�� Example Example –– A common approach to A common approach to

conductive tracking in printed electronics is conductive tracking in printed electronics is based on conductive silver inks.based on conductive silver inks.

�� Is this the right approach, or are other Is this the right approach, or are other materials more materials more ““sustainable sustainable ““

�� Various experts have maintained that the Various experts have maintained that the entire world supply of above ground ,refined entire world supply of above ground ,refined silver is about 300 million ouncessilver is about 300 million ounces

Others have estimated that above ground Others have estimated that above ground silver may be as large as 4 billion ounces, silver may be as large as 4 billion ounces,

�� A more sustainable alternative might be A more sustainable alternative might be based on aluminium based on aluminium ––

in its recycled form it in its recycled form it

only has embodied energy of 9 MJ/ kg, only has embodied energy of 9 MJ/ kg, �� --

and it is present in the earths crust in vast and it is present in the earths crust in vast

quantitiesquantities�� (But its oxide layer makes conductive ink (But its oxide layer makes conductive ink

formulation challenging)formulation challenging)

Is there enough oil left to power the Is there enough oil left to power the processes, and provide raw materials for processes, and provide raw materials for

organic electronics?organic electronics?�� In theory we have 50,000 years left of fossil In theory we have 50,000 years left of fossil

fuel deposited in the earths crustfuel deposited in the earths crust

�� (But it(But it’’s not accessible, and burning it would s not accessible, and burning it would use up all the oxygen in the atmosphere).use up all the oxygen in the atmosphere).

�� Accepting a 10% reduction in oxygen level Accepting a 10% reduction in oxygen level would allow 5,000 years of fossil fuel use.would allow 5,000 years of fossil fuel use.

Data from Data from ““Global Energy PerspectivesGlobal Energy Perspectives””

consumption Gtoe/pa resource base additional occurrencesoil conventional 3.2 295 -oil unconventional - 525 1 900gas conventional 1.7 420 -gas unconventional - 450 400methane hydrates - - 18 700

coal 2.2 3400 3000uranium 0.5 263 150U in fast breeder - 15 540 8900

Total 7.5 15958 33 050Source: Global Energy Perspectives

Prospects for Printed ElectronicsProspects for Printed Electronics

�� Printed Solar cells Printed Solar cells -- a route to low carbon energya route to low carbon energy

�� (Konarka cells offer 3(Konarka cells offer 3-- 5% efficiency , but ink jetted 5% efficiency , but ink jetted

cells only 1cm2 at present)cells only 1cm2 at present)

�� Printed Lighting Printed Lighting –– prospects of large area printed prospects of large area printed

lighting systems, perhaps with a factor 10 lighting systems, perhaps with a factor 10 improvement in efficiency over incandescent bulbsimprovement in efficiency over incandescent bulbs

�� Printed Batteries Printed Batteries -- more sustainable than current more sustainable than current

technology?technology?

Lithographically Printed Voltaic CellsLithographically Printed Voltaic CellsWhat?What?

•• Investigate the fabrication of voltaic cells (electric cells & Investigate the fabrication of voltaic cells (electric cells & batteries) by the offset lithographic printing processbatteries) by the offset lithographic printing process

Why?Why?

•• Offset lithography has been adapted to manufacture electronic Offset lithography has been adapted to manufacture electronic components and circuit interconnect on a wide range of flexible components and circuit interconnect on a wide range of flexible materials.materials.

•• Costly additional processes and materials required for powerCostly additional processes and materials required for power

•• Market surveys suggest that this is an obstacle to the potentialMarket surveys suggest that this is an obstacle to the potential

uptake of the technologyuptake of the technology

LPVC Project OverviewLPVC Project Overview

•• Work has been carried out on ink formulations suitable for offseWork has been carried out on ink formulations suitable for offset t lithography to enable the manufacture of Carbon Zinc cellslithography to enable the manufacture of Carbon Zinc cells

•• Voltaic cells have been manufactured and evaluatedVoltaic cells have been manufactured and evaluated

11stst Iteration CellsIteration Cells

1.5V but very low current1.5V but very low current…………..due to electrode resistance..due to electrode resistance

1.5 V achievable1.5 V achievable

2 nA current 2 nA current

Internal ResistanceInternal Resistance

Ra – the resistance of the electrochemical path including the electrolyte and the separatorRm - is the resistance of the metallic path through the cell including the terminals, electrodes and interconnect Cb - the capacitance of the parallel plates which form the electrodes of the cell. Ri - is the non-linear contact resistance between electrode and the electrolyte.

Simplified electrical model of cell

22ndnd Iteration Iteration --

Electrode Development Electrode Development

•• Anode and cathode structures printed on substrate over highly coAnode and cathode structures printed on substrate over highly conductive silver nductive silver base. Silver base layer employed as connection terminalsbase. Silver base layer employed as connection terminals

•• Membrane placed Membrane placed above electrolyteabove electrolyte

•• Zinc anode (Zinc anode (--) structure ) structure placed above membraneplaced above membrane

Typical Carbon Zinc Discharge Typical Carbon Zinc Discharge

Eveready Carbon Zinc (Zn/MnOEveready Carbon Zinc (Zn/MnO²²) ) Application Manual Application Manual Eveready Battery Co. Eveready Battery Co. Inc. Inc. 20012001

22ndnd Iteration Printed Cell CharacteristicsIteration Printed Cell Characteristics

Printed cell discharge curve through 1kPrinted cell discharge curve through 1kΩΩ

loadload

Printed cell discharge curve through 5kPrinted cell discharge curve through 5kΩΩ

continuous loadcontinuous load

33rdrd Iteration Printed Cell CharacteristicsIteration Printed Cell Characteristics

Current StructuresCurrent Structures

I.I.

LPVCsLPVCs

with with ‘‘usefuluseful’’

capacity demonstrated capacity demonstrated

II.II.

Manufacturing methods and activation mechanisms under Manufacturing methods and activation mechanisms under investigationinvestigation

Battery of LPVCspowering conventional electronic system

ConclusionsConclusions