Sustainable Manufacturing (PP5.1)

PP5.1: Sustainable Manufacturing

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This work package targets identifying material requirements for Terawatt scale PV deployment and critical material issues/bottlenecks that must be addressed.

 

From this, technology roadmaps towards sustainable TW scale PV manufacturing will be developed for existing and emerging solar cell technologies.

 

The work package will then focus on addressing critical material issues to improve the sustainability of manufacturing capacity, while ensuring low-cost. This will include modified cell structures, metallisation schemes and interconnection methods to reduce the reliance on critical materials, and also target designs to improve recyclability. 

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PP5.1.1 Critical Material Challenges 

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With rapid expansion of PV manufacturing expected over the coming decade towards TW scale PV manufacturing and potential cumulative installed PV capacity of 60 TWp by 2050, a key requirement for the industry is to rapidly identify critical material challenges across the whole PV value chain for existing and emerging solar cell and module technologies.

 

This package will perform a critical material assessment for existing industrial cell technologies (PERC, TOPCon and SHJ) and emerging thin-film and tandem technologies across the value chain.

 

This will cover: 1) the choice of bulk semiconductor material particularly for emerging thin-film technologies and tandem devices (eg. silicon, CdTe, GaAs, perovskite); 2) materials for passivating contacts and transparent conductive oxide layers for heterojunction solar cells and perovskites, and interlayers for tandems (particularly indium); 3) metal contacts such as silver; 4) low-temperature alloys for interconnection and other module materials (indium and bismuth); and 5) key balance of systems components such as steel, concrete, copper and aluminium.

 

Assessments will be based projected cell/module efficiencies, global material reserves and annual supply, and expected material requirements for other clean energy technologies. It will also consider the impact of module recycling, and length of operation in the field, as a possible method to alleviate future material demand. From the assessments, technology roadmaps will be developed, focusing on alignment with the ITRPV and identifying shortfalls in future roadmaps. This will closely link to PP5.1.2  to guide research.

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Objectives

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• Identify critical material issues at the cell, module and system level for PERC, TOPCon, SHJ as well as potential emerging thin-film and tandem technologies including silicon-based tandems.

• Develop technology roadmaps to achieve annual manufacturing capacities >1 TW per year for all main technologies listed in the ITRPV 2021 to 2030 (PERC, TOPCon, SHJ, back-contact and silicon-based tandems) and others as required, including critical materials (eg. silver, indium, bismuth) and key module/system materials including steel, concrete, aluminium, glass, copper.

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Investigators: Brett Hallam (UNSW), Anthony Chesman (CSIRO), Andrew Blakers (ANU)

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PP5.1.2  Modified Cell and Module Designs

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Work in this stream will draw on findings from PP5.1.1, to target device and module fabrication changes to increase the sustainable manufacturing capacity of the respective technologies, while ensuring high performance and low LCOE values.

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Cell level technology development: At the cell level, particular emphasis will be placed on developing approaches to reduce silver consumption, due to its dominance for screen-printed solar cell technologies, which is expected well into the future as stated in the 2021 ITRPV.

 

Work will focus on reducing silver consumption, to reduce silver consumption to 20% of global supply for a 3 TW market, 4x lower than the 2030 value for PERC in the 2021 ITRPV, investigating both screen printing alternative metallisation technologies like plating.

 

For tandems, work fill focus on two-terminal devices, for the unique opportunity to greatly reduce silver by a factor of up to six compared to PERC. Alternative silver-free and ultra-lean silver metallisation technologies like copper plating will be investigated.

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Next generation solar cells beyond PERC all feature passivated contacts. Such solar cells are also expected to form the bottom-cell of silicon-based tandems. Material challenges related to passivated contact solar cells will also be addressed.

 

Work will also focus on developing passivating contacts using materials sufficiently abundant for TW scale manufacturing. For thin-film and tandems, work will emphasise using abundant semiconductor materials and non-toxic materials, such as CZTS and avoiding the use of lead in perovskite materials, to reduce environmental impact.

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At the module level, work will focus on interconnection methods that can reduce the requirement for silver at the cell level, and also reduce the consumption of indium, bismuth and other scarce materials in low-temperature alloys, particularly for solar cells requiring low-temperature interconnection.

 

Work will investigate opportunities for holistic changes to cell metallisation and interconnection schemes for both screen-printed and plated cells, and opportunities for screen-printing and other patterning technologies to assist with the reduction of key materials such as bismuth, focusing on lead-free solders and silver-free electrically conductive adhesives.

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Another challenge at the module level is embedded energy. Despite being abundant, aluminium was recently identified as a material of concern by the World Bank due to its global warming potential for future growth of the PV industry.

 

Work will focus on module designs with lower aluminium usage reduced-frame or frame-less modules and changes to cell configurations. The stream will also develop low-weight modules to reduce emissions associated with transportation.

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Objectives

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• Fabricate a solar cell featuring at least one passivated contact with consumption of key materials sufficiently low to enable TW scale manufacturing

• Develop a solar cell structure featuring a transparent conductive oxide layer suitable for TW scale PV deployment

• Develop a contact geometry to reduce silver consumption using screen-printing

• Develop a low-temperature interconnection approach with bismuth consumption

• Develop a module-based milestone with low Al, large module, or light weight.

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PP5.1.3 Design for Recycling and End-of-Life

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With PV heading towards TW scales of manufacturing, electronic waste from PV is set to increase exponentially.

 

Given that modules have expected timeframes of operation in the field of 25+ years, it is critical to modify PV module and cell structures with end-of-life in mind to improve recyclability.

 

A key current challenge for recycling is the industry-dominating EVA (ethylene-vinyl-acetate) encapsulant material. This work will draw on challenges identified in PP5.5, to improve ease of recycling.

 

The work package will investigate alternative encapsulant materials with improved ability to recycle to enable recovery of precious elements from the solar cell structure, such as silver, copper and silicon.

 

Work will also investigate encapsulant-free module technologies such as the New Industrial Solar Cell Encapsulation (N.I.C.E) technology from Apollon Solar, a partner in the program, and how to fabricate emerging high-efficiency solar cell technologies to be compatible with such module technology, that are designed with ease of disassembly and recycling in mind.

 

Modified cell architectures will also be developed to integrate with module technologies for improved recyclability such as copper plated contacts, and as an option to avoid a lack of silver recovery as cell technologies push towards lower silver consumptions, which could affect the economics of recycling.

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Objectives

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• Fabricate a PV module featuring solar cells with low silver consumption that can be readily disassembled for recycling.

• Evaluate the use of encapsulants other than EVA

• Fabricate a PV module featuring no encapsulant 

• Evaluate potential barriers in manufacturing the PV modules