Coating method paves way for large-scale perovskite solar cell production

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A new dipping process using a sulfolane additive creates high-performing perovskite solar cells. The method is inexpensive and well-suited for scaling up to commercial production. (Image: LANL)

A new coating method added to perovskite solar cell production overcomes the key bottleneck to large-scale production and commercialisation of the promising perovskite technology.

Researchers from National Taiwan University (NTU) and Los Almos National Laboratory (LANL) in the US say the work paves the way for low-cost, high-throughput commercial-scale production of large-scale solar modules in the near future.

Perovskite photovoltaics, seen as a viable competitor to the familiar silicon-based photovoltaics on the market for decades, have been a highly anticipated emerging technology in the last decade.

Commercialisation has been stymied by the lack of a solution to the field’s grand challenge: scaling up production of high-efficiency perovskite solar cell modules from the bench-top to the factory floor.

The team invented a one-step spin coating method by introducing sulfolane as an additive in the perovskite precursor, or the liquid material that creates the perovskite crystal through a chemical reaction. As in other fabrication methods, that crystal is then deposited on a substrate.

The new process, described in Joule in March, allowed the team to produce high-yield, large-area photovoltaic devices that are highly efficient in creating power from sunlight. These perovskite solar cells also have a long operational lifetime.

Through a simple dipping method, the team was able to deposit a uniform, high-quality perovskite crystalline thin film covering a large active area in two mini-modules, one of about 16cm2, the other nearly 37cm2. Fabricating uniform thin film across the entire photovoltaic module’s area is essential to device performance.

Wanyi Nie, a research scientist fellow at LANL’s Center of Integrated Nanotechnologies, said: ‘We were able to demonstrate the approach through two mini-modules that reached champion levels of converting sunlight to power, with greatly extended operational lifetimes. Since this process is facile and low-cost, we believe it can be easily adapted to scalable fabrication in industrial settings.’

The mini modules achieved a power conversion efficiency of 17.58 per cent and 16.06 per cent, respectively, among the highest reported to date. The power conversion efficiency is a measure of how effectively sunlight is converted into electricity.

For other perovskite fabrication methods, one of the major roadblocks to industrial-scale fabrication is their narrow processing window, the time during which the film can be laid down on the substrate. To get a uniform crystalline film that’s well bonded to the layer below it, the deposition process has to be strictly controlled within a matter of seconds.
Using sulfolane in the perovskite precursor extends the processing window from 9 to 90 seconds, forming highly crystalline, compact layers over a large area, while being less dependent on the processing conditions.

The sulfolane method can be easily adapted to existing industrial fabrication techniques, which helps to pave the path towards commercialisation.

A perovskite is any material with a particular crystal structure similar to the mineral perovskite. Perovskites can be engineered and fabricated in extremely thin films, which makes them useful for solar photovoltaic cells.

Flexible solar film introduced in rural Africa and India

Power Roll has installed two flexible solar photovoltaic mini grid systems in rural locations in Africa and India, as highlighted in a recent case study published by Innovate UK.

The solar film is low-cost, light, easy to install and can be used off-grid. At scale, Power Roll’s technology will produce electricity at a cost of $0.03/watt manufactured, at least 40 per cent cheaper than silicon PV, the company says. It weighs 0.3kg/m², which is as little as 2 per cent of current silicon PV products, according to Power Roll. The technology also requires no rare earth materials.

The systems have been installed in Africa and India as part of a trial supported by Innovate UK. It will help evaluate the performance of Power Roll’s solar film to help scale-up and commercialise its technology further.

Paul Laidler, project lead at Power Roll, explained: ‘Until now it’s been about proving the technology, but now we are measuring what difference it can make to people’s lives; for example, allowing women entrepreneurs to expand their business and making it easier for kids to learn, because they can study at night.’

The solar film will be produced as a roll and can be used on a variety of surfaces in off-grid settings; for example, curved around a technology pole or attached to a fragile roof. Its lightness and versatility provide advantages over silicon solar panels, not only where it can be deployed, but also in ease of transport.

The technology can be applied in a number of ways in off-grid settings, including lighting, charging laptops and mobile phones, and pumping water for irrigation purposes.

Laidler said: ‘We want to make solar energy affordable and available to everyone – that means a low-cost solution that works in off-grid locations where people have previously found it difficult to access power.’

Although the programme is concentrating on such locations in developing countries, Laidler says the mini grids could be installed anywhere – including in the underdeveloped commercial rooftop market – enabling solar power to be generated where not possible today.

The technology will also help the UK achieve its target of being net zero by 2050. Through investment from Finance Durham and other investors, Power Roll is constructing a pilot plant in County Durham, UK, to further scale-up and commercialise the technology.

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