High Efficiency CuInSe2 Photovoltaic Modules Deposited at Low Temperature by High Power Impulse Magnetron Sputtering (HIPIMS)

To be sustainable, energy in our homes and transport needs to be supplied from an inexhaustible source which does not pollute the environment. One such source has been present in our lives since before the formation of planet Earth and will continue to exist for hundreds of thousands of years - it is, of course, the Sun. The light from the sun can be used to make electricity with a solar cell. Every roof top and wall which is lit by the sun can be covered with solar panels and potentially used to make energy. Industry often makes solar cells by taking an everyday material such as glass and coating it with thin layers of semiconductor materials (called absorbers) which absorb light and convert it to electricity.

Our research aim is to invent a brand new method for producing solar cell coatings and improve our understanding of the layers. The new method will make solar cells more affordable by using less raw materials and less power during manufacture. It will be applicable to semiconductor materials of today and the future.

The new method is based on a technology called HIPIMS (which stands for High Power Impulse Magnetron Sputtering) and is a very recent addition to a family of "plasma" techniques, in which the coating is produced by bombarding the surface you want to coat with carefully prepared atoms and ions. HIPIMS was first discovered in 1995, and pioneering work in our group and elsewhere has already shown that it produces an excellent plasma, with a combination of ion properties which should produce highly efficient solar cells. Our group was the first to use HIPIMS to make solar cells and our early trials do indeed turn out to be very promising.

Because it is so new, there are a number of key features of making solar cells by HIPIMS which we do not yet understand. HIPIMS produces a great range of unique and unusual plasmas which create different structures of layers. We are planning to focus our efforts on understanding the link between plasma, structure of the layer and its efficiency in converting light to electricity. Answering these questions would be of interest to scientists who study plasmas, and would help technologists to learn how to apply HIPIMS to create new, better coatings.

In the research we will measure properties of HIPIMS plasmas to understand how the composition of the plasma can be changed. We will do this by extracting particles from the plasma and carefully analysing their mass and energy. We will also make coatings using HIPIMS and measure their properties (for example how efficient they are) and examine them under electron microscopes to help our understanding of how the properties relate to the microscopic structure produced by the HIPIMS plasma. In the final stages we will produce large cells in machines used in industry to demonstrate the usefulness of the process not only in science but in business as well.

Our experience and understanding should help industrialists to develop manufacturing processes which can generate new, better solar cells. In a few years our houses, cars and mobile phones may all be powered by solar cells developed using HIPIMS!

The beneficiaries of the project results are manufacturers within the photovoltaic sector. In particular they include manufacturers of machines for production of thin film solar cells and manufacturers of the thin film modules themselves.

Photovoltaic development roadmaps in EU, Japan and USA have all set efficiency targets of 25% for CIGS-based modules compared to today's ~13% in production. It is unlikely that these targets will be met solely by improvement of existing technologies. New production techniques are required to widen the range of available manufacturing parameters and make full scale modules with conversion efficiencies approaching those achieved on lab scale.

The project will develop a new technology for manufacturing of CIGS-based photovoltaic modules with high efficiency and at low temperature. The technology has a high flexibility in the types of layer structures it can produce. Early upscaling trials have been successful. As such it holds a promise of closing the gap between research and industrial production.

The new technology will allow manufacturers to remain competitive in the fast growing photovoltaics market by reaching high module efficiencies. The proposed technology will reduce production energy requirements and manufacturing costs due to its low process temperature. It will reduce usage of raw material due to its high efficiency of material utilisation.

The project outcomes will contribute to environmental sustainability as they directly address the issue of fully clean energy production.

The technology will be of interest to industry due to its potential to lower cost by increasing productivity and raising material utilisation efficiency. It also offers lower process temperatures, which could enable to combine CIS with other types of cells to produce multiple bandgaps and higher efficiency.

The project will provide opportunities for commercialisation of new technology, exploitation of accumulated scientific knowledge and create new processes and products on the market. The new technology has a high potential for commercialisation. New products would be introduced by machine-building companies such as VAAT, who would be able to design new machines or retrofit the technology in existing machines. New process monitoring strategies will be developed allowing companies such as Gencoa to introduce new products based on this. New processes may be introduced by suppliers to the solar module industry such as Pilkington who will be able to offer lower price products on account of reduced manufacturing costs - including less energy and raw material consumption. New sputtering targets may be developed and introduced to market by suppliers such as GfE to support the implementation of the new technology. Specifications for new analytical instrumentation such as the plasma sampling mass spectrometer built by Hiden Analytical to study and monitor deposition processes will become clear during the research.

The economic impact of the project will foster performance and competitiveness of companies in UK and Europe. Solar energy is recognised as one of the most probable candidates to alleviating energy shortage and dependency. Government policies across Europe and developed countries push for increased solar capacity. In this climate, the photovoltaics manufacturing business is growing at a fast pace and is extremely competitive. Industry in UK and Europe has recognised that it requires new technology to stay competitive. This proposal aims to answer this need by developing an industrially viable new technology for the production of photovoltaic cells.

The project outcomes will contribute to environmental sustainability as they directly address the issue of fully clean energy production by solar cells and a green production of the photovoltaics themselves.