"Solar power has disrupted the future of renewable energy. As photovoltaic technology blazes a trail to cheaper, cleaner electricity, the UK now has the potential to power 100 million LED bulbs at once," writes Professor Joe Briscoe, Professor of Energy Materials and Devices.
That’s because solar cells, one of the first methods of generating renewable energy to be utilised on a large scale, have steadily become more efficient. Innovations in silicon technology, the leading material in solar cell manufacturing, can now enable over 23% of solar energy to be converted into electricity. But with power demand rising fast, we’re reaching the limits of power conversion efficiency with silicon.
So how do we keep upgrading solar power for the future?
My team and I are investigating how innovative manufacturing techniques are enabling the production of a new kind of solar cells made from perovskite – a crystallized organic-inorganic hybrid compound.
Our research is helping improve and optimize the production and operation of perovskite solar technology. With a new aerosol-based treatment, we can make these new solar cells an even more affordable and efficient option, helping solar power continue to boost our renewable energy progress across the UK.
The efficiency problem
As the traditional material for solar panel manufacturing, silicon makes up 90% of the solar cells in use today. But upgrading these cells beyond the current efficiency is becoming increasingly difficult as they approach their maximum theoretical efficiency limit.
That’s where perovskite comes in. A combination of lead, halide, and organic molecules, it can be formed from a chemical solution and then annealed (heated and cooled slowly) at a much lower temperature than it takes to work with silicon – only 100-150°C compared to over 1,400°C for silicon. This makes it cheaper to produce, and easier to work with.
Initially less efficient than silicon, perovskite solar cells have undergone significant improvements, and now boast a solar energy conversion efficiency of over 25% - comparable to that of the best small area silicon cells.
However, challenges persist. The low-temperature, solution-based nature of the manufacturing process for perovskites leads to a high number of flaws in the material, especially when manufactured over large areas. The cells themselves are also susceptible to decomposition when exposed to moisture and oxygen, which severely limits perovskite’s commercial viability.
Addressing these challenges is crucial for perovskites to emerge as a commercially competitive technology and requires innovative new manufacturing methods.
Perfecting a new processing method
To overcome these hurdles, and produce new ways to produce solar, the team and I have explored a novel method known as aerosol-assisted solvent treatment. This technique involves passing an aerosol over a surface in a controlled manner before passing through a reactor containing the heated perovskite sample.
The aerosolized solution, in our case a dimethylformamide (DMF) solution alone or with added methylammonium chloride (MACI), significantly enhances the grain growth of perovskite cells, reducing local defects and improving overall uniformity. The process itself takes no more than five minutes and can also facilitate processing some perovskites at a lower temperature (100 degrees C) compared to direct thermal annealing.
The treated perovskite cells exhibit remarkable performance improvements, with increased efficiency and stability across various compositions, device structures, and areas. And it also makes these cells more affordable and easier to mass-manufacture.
Moreover, this process extends its applicability to photodetectors, resulting in enhanced low light photo-response which makes them almost twice as efficient in low light conditions - crucial for both photodetectors and solar cells in regions with limited sunlight. This means that perovskite cells don’t just improve upon existing technology, but also provide exciting new methods for solar power generation.
Breaking the efficiency ceiling
The potential applications of this improved technology are vast. Aerosol-enhanced perovskite cells can be printed onto plastic sheets, enabling these cells to be implemented in new ways, such as indoor locations, self-powered consumer electronics, car ports, building exteriors, and even integration into electric vehicles.
Beyond this, there is another major advantage of perovskite materials: their chemical composition can be changed to ‘tune’ the colour of light that they absorb. This means that perovskites can be made to absorb the blue end of the spectrum – where a lot of the energy loss comes from in silicon solar cells – and pass through the red and infra-red light. These can then be stacked on top of silicon cells to make a ‘tandem’ design, boosting the overall efficiency of the solar panels to nearly 30%.
This is a major step change compared to silicon alone, with efficiencies of over 30% possible in the future. Therefore, these tandem solar cells could massively increase the power produced by solar panels at little additional cost.
Shedding new light on solar power
Looking ahead, our team is conducting further tests to assess the long-term effectiveness of this process and its scalability for commercial applications. We envision optimizing the aerosol-assisted solvent treatment in a large-area reactor, paving the way for the development of cost-effective, lightweight, and flexible solar cells at a commercial scale.
In line with our commitment to real-world impact, my team is also launching a spinout company, AeroSolar, which received £50,000 from Innovate UK to build a large-scale reactor, which has now been completed and is undergoing testing. We are actively collaborating with perovskite solar cell manufacturers and attracting interest from investors to help identify the impact of these new use cases.
The perovskite solar cell market is projected to reach US$1.2 billion by 2033, underscoring the immense potential of our research in shaping the future of solar energy.
The potential of this new manufacturing method is enormous – these new innovations mean low-cost, high-efficiency solar power can enable the continued progress of renewable energy for a more sustainable future.
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