Imagine a skyscraper powered entirely by solar electricity? This dream is not far off, if thin film solar cells technology flies. Thin film solar cells are a new type of solar cells consisting of multilayer structures built on glass.
Compared to conventional crystalline silicon solar cells, thin film cells only use one hundredth the silicon, which significantly reduces the cost. Moreover, thin film solar cells can be readily installed onto the roofs of buildings, or integrated into the wall to replace the glass windows, making them very attractive for building sectors.
However, one of the critical challenges the thin film solar cell faces is the low energy conversion efficiency due to the insufficient absorption from the very thin silicon layer.
In 2010 the Victoria-Suntech Advanced Solar Facility (VSASF) was established to focus on solutions to overcome the efficiency limitations of thin-film solar cells through the research and development of nanoplasmonic solar cells.
The 12 million VSASF was jointly funded by Swinburne University of Technology, the Victorian State Government and Suntech Power Holdings Co, Ltd., the world’s largest solar panel manufacturer. Its initiative shares the vision of NANOPLAS technology, a patented revolutionary solar cell technology developed at the VSASF for a sustainable energy future. Our research focuses on the integration of nanostructures and nanomaterials that can be directly applied to conventional thin film solar cells to manipulate and control light by light scattering and concentrating effects.
The NanoPlas solar cell works by incorporating a thin layer of metallic nanoparticles into the conventional thin film solar cells to effectively scatter light into the cells. This increases the amount of light entering the cells, improving the conversion of light into electricity. In the recently published Nano Letters paper we went one step further by using what are known as nucleated or ‘lumpy’ nanoparticles.
Left: A sample of the thin film solar cell, which can transmit solar light. Middle: schematic of NanoPlas solar cell integrated with the lumpy nanoparticles. Right: schematic of how the lumpy nanoparticles can scatter light of a wide spectral range.
What we have found is that nanoparticles that have an uneven surface scatter light even further into a broadband wavelength range with large scattering angles ensuring the light to be well-trapped in the cells. This leads to a greatly enhanced absorption, and therefore significantly improves the cell’s overall efficiency.
Compared with conventional thin film solar cells, the lumpy nanoparticle integrated solar cells are almost 25 per cent more efficient. Although still in its earlier stage of laboratory testing, advantages of this type of solar cells are obvious, including broadband absorption of light spectra from the sun leading to higher conversion efficiency; the simple and low cost fabrication method that can be easily integrated into the current solar cell manufacturing process without inducing much extra cost; the technology enables even less silicon to be used compared to the conventional thin film solar cells, further reducing the cost. Optimisation of the NanoPlas technology can potentially allow a doubling the efficiency of existing solar cells whilst halving the manufacturing cost.
Integrating solar cells with buildings is a very attractive concept for building sectors because it allows skyscrapers to self-power themselves with purely green solar energy, providing a sustainable solution for the building sector.
The NanoPlas thin film technology can be directly integrated into building glass like a tint layer converting normal windows into solar cells. This means that there won’t be any sacrifice from the architectural point of view since the solar cells look like normal glass.
The transparency of the solar cell window can be adjusted by the advanced laser scribing technology. And the size of the solar cells can be scaled up to several square metres. Based on the current efficiency of the NanoPlas technology, one sqm of solar cell can produce 90 W electricity. This means a normal seven storey building can have the power capacity of 0.75 MW. And it can produce annual electricity of 740 MWh, reducing the CO2 generation of 970 tonnes. The electricity generated can power 4000 20 W light bulbs.
The NanoPlas technology addresses the biggest challenge of the thin film solar cells: the cost-effectiveness, making building-integratable solar cells a more viable technology for the building sector. We believe the NanoPlas technology can make a difference to Australian solar manufacturers through further research and development to scale up the technology. With the NanoPlas technology, thin film solar cells can light the future with skyscrapers powered entirely by sunlight, transforming our cities.
Professor Min Gu, FAA, FTSE, FSPIE, FOSA, FInstP, FAIP, Australian Laureate Fellow, is Director of Centre for Micro-Photonics at Swinburne University of Technology.
