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Aust breakthrough could transform solar PV

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30 Jan, 2025

This post was originally published on Sustainability Matters

UNSW Sydney researchers have made an important breakthrough that could transform photovoltaic technology, making solar cells more environmentally friendly, cost-effective and efficient.

The scientists, from UNSW’s School of Photovoltaic and Renewable Energy Engineering, managed to achieve a best-ever efficiency of 13.2% for high bandgap kesterite solar cells.

While kesterite is a naturally occurring mineral, it can also be artificially created at low cost by combining copper, zinc, tin and sulfur — all abundant, non-toxic materials. Taking its name from these component parts, synthesised kesterite is known as CZTS.

CZTS is a promising material for future generations of solar cells because it is environmentally friendly, relatively inexpensive to manufacture and known to maintain its photovoltaic performance over a long period of time. However, it hasn’t been widely adopted at this stage because it is subject to defects during production, hampering its efficiency.

Led by Scientia Professor Xiaojing Hao, the UNSW team has helped to solve this problem by annealing, or heat-treating, the CZTS solar cell device in a hydrogen-containing atmosphere. The fundamental research behind the record-breaking efficiencies, which first achieved 11.4% after six years of stagnation for CZTS, has now been published in the journal Nature Energy.

The record-breaking kesterite solar cell developed at UNSW. Photo: UNSW Sydney.

“The big picture here is that we ultimately want to make electricity cheaper and greener to generate,” Hao said.

“Silicon modules have almost reached the limit of their theoretical efficiency, so what we are trying to do is answer the question coming from the PV industry as to what the next generation of cells will be made of.

“And as well as that, how can we make solar panels less expensive to manufacture, and how can we get more electricity per area so the panels can be particularly beneficial for area-limited PV applications?”

Passivating effect of hydrogen

Before the team’s breakthrough, the maximum photovoltaic efficiency of CZTS had been stuck at 11% for the past six years. Now, they expect their use of hydrogen during production to advance CZTS’s efficiency even further.

“In basic terms, to create CZTS you take copper, tin, zinc and sulfur and ‘cook’ them all together at a certain temperature which turns it into a material you can use as a semiconductor,” Hao said.

“The tricky part is controlling the defects that are introduced during that process. What we have shown in this work is that introducing hydrogen can ensure those defects have less of an impact — which is known as passivation.

“Because hydrogen is modulating the defects within CZTS, that’s what helps increase its efficiency in terms of converting sunlight into electricity.”

Tandem solar

CZTS could be best implemented in what are known as tandem solar cells, which combine two or more solar cells to capture and convert more of the solar spectrum into electricity, improving overall efficiency.

Hao is hopeful that the new breakthrough will accelerate the chances of CZTS reaching 15% efficiency within the next year, and expects its commercialisation by 2030.

“There is still work to be done to find ways to further reduce the defects we find in CZTS, either during the fabrication or via post-fabrication treatments,” she said.

“But we know that this is a good material. When we consider the requirements from the bottom up, we know that we need something that is widely abundant, that is environmentally friendly, that has good optoelectronic properties and can last a long time — and CZTS fits the bill.”

Other tandem options

Hao and her team are also conducting research into another potential material that could partner with silicon: perovskite.

While perovskite is significantly more efficient (close to 27% in small-area examples) in converting the sun’s energy into electricity, it degrades quickly and contains highly toxic components that can dissolve in water, such as lead.

When considering perovskite, Hao said, “you can get really high performance and high efficiency at the beginning, but it’s much less stable and the panels might only last for one year, so it’s not sustainable”.

“It can take a long time to solve those problems, whereas with CZTS if we can get it to 20% efficiency then I think it will really take off because there are no other limitations since it meets all the criteria for the type of material we want to be using,” she added.

“Overall, I think we should be looking into all different types of materials for the top layer of tandem cells. That’s the only way we can maximise our chances of success and accelerate the speed towards obtaining highly efficient tandems that we can use long into the future.”

Top image caption: The UNSW research team with the record-breaking kesterite solar cell. Pictured are Dr Jialiang Huang, Dr Kaiwen Sun, Scientia Professor Xiaojing Hao and Ao Wang. Photo: UNSW Sydney.

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Taking the electronic pulse of the circular economy

Taking the electronic pulse of the circular economy

In June, I had the privilege of attending the 2025 E-Waste World, Battery Recycling, Metal Recycling, and ITAD & Circular Electronics Conference & Expo events in Frankfurt, Germany.

Speaking in the ITAD & Circular Electronics track on a panel with global Circular Economy leaders from Foxway Group, ERI and HP, we explored the evolving role of IT asset disposition (ITAD) and opportunities in the circular electronics economy.

The event’s focus on advancing circular economy goals and reducing environmental impact delivered a series of insights and learnings. From this assembly of international expertise across 75+ countries, here are some points from the presentations that stood out for me:

1. Environmental impact of the digital economy

Digitalisation has a heavy material footprint in the production phase, and lifecycle thinking needs to guide every product decision. Consider that 81% of the energy a laptop uses in its lifetime is consumed during manufacture (1 tonne in manufacture is equal to 10,000 tonnes of CO2) and laptops are typically refreshed or replaced by companies every 3–4 years.

From 2018 to 2023, the average number of devices and connections per capita in the world increased by 50% (2.4 to 3.6). In North America (8.2 to 13.4) and Western Europe (5.6 to 9.4), this almost doubled. In 1960, only 10 periodic table elements were used to make phones. In 1990, 27 elements were used and now over 60 elements are used to build the smartphones that we have become so reliant on.

A key challenge is that low-carbon and digital technologies largely compete for the same minerals. Material resource extraction could increase 60% between 2020 and 2060, while demand for lithium, cobalt and graphite is expected to rise by 500% until 2050.

High growth in ICT demand and Internet requires more attention to the environmental footprint of the digital economy. Energy consumption of data centres is expected to more than double by 2026. The electronics industry accounts for over 4% of global GHG — and digitalisation-related waste is growing, with skewed impacts on developing countries.

E-waste is rising five times faster than recycling — 1 tonne of e-waste has a carbon footprint of 2 tonnes. Today’s solution? ‘Bury it or burn it.’ In terms of spent emissions, waste and the costs associated with end-of-life liabilities, PCBAs (printed circuit board assembly) cost us enormously — they generally achieve 3–5% recyclability (75% of CO2 in PCBAs is from components).

2. Regulating circularity in electronics

There is good momentum across jurisdictions in right-to-repair, design and labelling regulations; recycling targets; and voluntary frameworks on circularity and eco-design.

The EU is at the forefront. EU legislation is lifting the ICT aftermarket, providing new opportunities for IT asset disposition (ITAD) businesses. To get a sense, the global market for electronics recycling is estimated to grow from $37 billion to $108 billion (2022–2030). The value of refurbished electronics is estimated to increase from $85.9 billion to $262.2 billion (2022–2032). Strikingly, 40% of companies do not have a formal ITAD strategy in place.

Significantly, the EU is rethinking its Waste Electrical and Electronic Equipment (WEEE) management targets, aligned with upcoming circularity and WEEE legislation, as part of efforts to foster the circular economy. A more robust and realistic circularity-driven approach to setting collection targets would better reflect various factors including long lifespans of electronic products and market fluctuations.

Australia and New Zealand lag the EU’s comprehensive e-waste mandated frameworks. The lack of a systematic approach results in environmental degradation and missed positioning opportunities for businesses in the circular economy. While Australia’s Senate inquiry into waste reduction and recycling recommended legislating a full circular economy framework — including for imported and local product design, financial incentives and regulatory enforcement, New Zealand remains the only OECD country without a national scheme to manage e-waste.

3. Extending product lifecycles

Along with data security and digital tools, reuse was a key theme in the ITAD & Circular Electronics track of the conference. The sustainable tech company that I lead, Greenbox, recognises that reuse is the simplest circular strategy. Devices that are still functional undergo refurbishment and are reintroduced into the market, reducing new production need and conserving valuable resources.

Conference presenters highlighted how repair over replacement is being legislated as a right in jurisdictions around the world. Resources are saved, costs are lowered, product life is extended, and people and organisations are empowered to support a greener future. It was pointed out that just 43% of countries have recycling policies, 17% of global waste is formally recycled, and less than 1% of global e-waste is formally repaired and reused.

Right to repair is a rising wave in the circular economy, and legislation is one way that civil society is pushing back on programmed obsolescence. Its global momentum continues at different speeds for different product categories — from the recent EU mandates to multiple US state bills (and some laws) through to repair and reuse steps in India, Canada, Australia and New Zealand.

The European Commission’s Joint Research Commission has done a scoping study to identify product groups under the Ecodesign framework that would be most relevant for implementing an EU-wide product reparability scoring system.

Attending this event with the entire electronic waste recycling supply chain — from peers and partners to suppliers and customers — underscored the importance of sharing best practices to address the environmental challenges that increased hardware proliferation and complex related issues are having on the world.

Ross Thompson is Group CEO of sustainability, data management and technology asset lifecycle management market leader Greenbox. With facilities in Brisbane, Sydney, Melbourne, Canberra, Auckland, Wellington and Christchurch, Greenbox Group provides customers all over the world a carbon-neutral supply chain for IT equipment to reduce their carbon footprint by actively managing their environmental, social and governance obligations.

Image credit: iStock.com/Mustafa Ovec

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