Polymer / fullerene photovoltaic devices: new materials and innovative processes for high-volume manufacture

Lead Research Organisation: University of Sheffield
Department Name: Physics and Astronomy


The harvesting of sunlight has the potential to revolutionize the way mankind generates electricity. At present however, only a small fraction (0.02% in 2008) of the world's total electrical power is generated using sunlight. Photovoltaic (PV) installations based on crystalline silicon are an increasingly popular way of generating electricity from solar-radiation, however such installations suffer from a relatively long pay-back time resulting from their high cost of manufacture. There is thus growing interest in the development photovoltaics based on organic (polymeric) materials (OPV) that can in principle be produced at low-cost, over very large areas utilizing solution-based processes that do not require a large energy input. At present however, even the best lab-based OPVs have an efficiency that is significantly lower than that of standard crystalline silicon (~8% compared with ~18%), coupled with a relatively short operational lifetime - attributes that have partly precluded their commercialization. There is nevertheless great interest in exploring the scale-up of OPVs, despite the fact that no common consensus has been reached on the best route to deposit multilayer architectures at high-speed. This problem is compounded by the fact that many of the materials that have the highest efficiency in OPV devices often have rather low solubility; properties that limit their application in high-speed manufacture processes. Addressing these issues lies at the heart of our proposed research. Firstly, we will engineer the chemical structure of state-of-the-art low energy-gap donor polymers to significantly improve their solubility and processability. We will then explore the deposition of such materials into OPVs using spray-based techniques. The thin-films formed will be characterized using high-resolution electron microscopy together with X-ray and neutron-scattering. The project team we have assembled for this task have leading expertise in organic-electronics, polymer-synthesis, polymer-physics and practical manufacturing processes. Our project is significantly strengthened by funds from the European Regional Development Fund (Project Mercury) to purchase an automated aerosol deposition system and fund postdoctoral and postgraduate researchers. We have ready route for commercialization via our (unfunded) links with a TSB-funded project that intends to develop OPVs for transparent window-glass applications. We anticipate the outcome of our work will be a materials set and a scalable process for high speed OPV manufacture.We will gain impact for our work through showcasing scaled-up OPV devices at the Sheffield Solar Farm and by interacting with artists and designers who wish to use organic photovoltaics in their work. We will also gain valuable support and publicity for our work through 'Project Sunshine'; a flagship project at Sheffield that promotes research into the utilization of solar energy to solve problems related to mankind's growing energy-needs and food-production in a time of growing climate uncertainty.

Planned Impact

There are significant commercial opportunities for the development and manufacture of solution-processable photovoltaic devices. These range to fully-flexible panels, to building-integrated systems. There is presently a window of opportunity for the development of valuable IP and enabling technology in this area that the UK must exploit in the face of significant international competition. Our project directly addresses the development of a high-volume manufacturable process to create organic photovoltaic (OPV) devices and will be important for driving new industrial opportunities. We are working informally with a TSB-funded consortium comprising PETEC, Pilkington, Polysolar and Solvay Ltd who are looking to manufacture semi-transparent OPV on window glass. Our work will provide basic underpinning science to this consortium, and will therefore find a very natural route to commercialization. In addition to the commercial opportunities of OPV manufacture, there are significant societal benefits to our work. Many rural communities in Africa, India and Latin America do not have access to electricity via a grid system as a result of limited basic infrastructure or unfavourable geographic location. The widespread deployment of cheap, light-weight, flexible and rugged photovoltaic panels to such disadvantaged communities could, for example provide refrigeration of medicines in remote clinics, or light for children to read and study in the evening. Enabling such communities to generate their own solar electricity could therefore be a very significant driver to reduce poverty and drive economic development. Low-cost PV panels that can be manufactured in large volumes are also an attractive proposition for people in developed countries, as they offer the potential for significant savings in domestic energy bills, and could also contribute to reduced CO2 emissions. The project will also have impact on a much shorter timescale through the high-level training that it will offer to the PDRAs and PG students that we will employ. Training will be in the areas of chemical synthesis of conjugated polymers, materials science including characterization and the fabrication and evaluation of photovoltaic devices. Given the very significant interest in photovoltaics (and materials research more broadly), the demand for researchers having such skills is likely to be high. The Faculty of Science at the University of Sheffield have shown very strong commitment to solar-energy research via its flagship project called 'Project Sunshine' and we will naturally gain national and international publicity as a result. Our proposed project will be closely linked to a PV research station called the Sheffield Solar Farm (SSF). The SSF will act as a demonstration centre for new and emerging photovoltaic technologies and will host a number of open days each year for schoolchildren and the general public. The SSF has a web-site that displays the current power output and efficiencies of all the PV devices currently under-test, together with a log of their performance. We will site the best spray-coated OPV modules developed in the project at the SSF. This will offer an excellent opportunity for us to show-case our OPV devices to the public and to a wide-range of potential industrial partners. We will collaborate with dress designers and sculptors who are interested in using flexible organic photovoltaics in clothing and jewelry. We are confident that this will attract mainstream media attention. We have an excellent track record in publishing research in high-impact journals, and we believe that the academic impact of our work will be high as our project combines basic physics, synthetic chemistry, material science with the development of practical manufacturing techniques. All the senior academic staff in our consortium have a significant media profile and will work actively in taking our research talks into schools and the local community.


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Zhang Y (2015) High efficiency arrays of polymer solar cells fabricated by spray-coating in air in Progress in Photovoltaics: Research and Applications

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Zhang Y (2018) Effect of fullerene acceptor on the performance of solar cells based on PffBT4T-2OD. in Physical chemistry chemical physics : PCCP

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Yang L (2016) Recent progress and challenges of organometal halide perovskite solar cells. in Reports on progress in physics. Physical Society (Great Britain)

Description We have developed a series of air-based spray-casting techniques to fabricate solar cells based on thin films of plastic. These were use to create a series of different devices that we characterized in detail. In our work, we made some of the most efficient devices yes reported using such spray-coating techniques.
Exploitation Route We have been working with a UK company for some time who wishes to start producing photovoltaic devices using the technologies that we have developed.
Sectors Creative Economy,Electronics,Energy,Manufacturing, including Industrial Biotechology,Retail

Description The work started in this project represented the first attempt to fabricate photovoltaic devices using a simple spray coating process. Subsequently, we have continued to develop these ideas and have explored spray coating photovoltaic devices using different semiconductor materials, and in particular a class of material called a perovskite. Our work on this topic has since expanded, and for the past few years, we have been working with a UK company called Power Roll Ltd to help them develop commercial products based on the technology that we first developed in this research. Since starting work with Power Roll, the links and activities between the Electronic and Photonic Molecular (EPMM) Group at Sheffield and Power Roll have grown significantly, with a very strong and enduring research partnership now established. This has been facilitated through number of rounds of Power Roll contract research funding (at full-FEC) supporting research at Sheffield, and through funding from University of Sheffield's various EPSRC IAA calls. Although Power Roll's initial interest was in the use fo spray-coating to fabricate photovoltaics, it was quickly found that the EPMM group could help the company validate many of the basic ideas behind their new technology. Here, Power Roll had a patented concept called a V-groove photovoltaic device (solar cell). Their idea is to laminate a micron wide, V-shape groove into a plastic sheet. By selectively patterning electrical contacts on either wall of the groove and then filling the groove with a light-absorbing semiconductor, it should be possible to make such a 'device' absorb sunlight and produce electrical power. By connecting thousands of such grooves in series, it is expected that this would act as a low cost and fully flexible solar cell device. The EPMM group at Sheffield has helped Power Roll validate their technology concept and we worked on a basic materials set to realise working devices. Since this initial work, the EPMM group has continued to work with the company, helping them explore and optimise new materials for electrical-charge extraction. This has been a rewarding experience, and we now have a selection of different metal oxide materials that work in devices. Power Roll have recently agreed to fund more work at Sheffield (matching a recent EPSRC / U Sheffield NPIF call), where we will explore the deposition in tin-oxide for solar cells via ion-assisted e-beam deposition. We believe that this technique will be a critical component of a practical and rapid manufacture process that will eventually allow Power Roll to produce their devices at scale. The EPMM - Power Roll collaboration has proved very beneficial for both partners; it has allowed EPMM to publish some interesting papers on this new type of solar cell architecture, with follow-up papers on materials processing either already published or being planned. It has also contributed very strongly to the career of the postdocs who have worked on this project. The collaboration has also proved very useful for Power Roll, as it would have been very difficult for the company to validate their concepts without input from Sheffield. This validation and continued working partnership has allowed the company to raise a number of rounds of venture capital funding and maintain their research workforce in NE England.
First Year Of Impact 2015
Sector Energy,Manufacturing, including Industrial Biotechology
Impact Types Economic

Description Research contract to develop back-contact perovskite solar cells (Power Roll Ltd)
Amount £250,000 (GBP)
Organisation Power Roll Ltd 
Sector Private
Country United Kingdom
Start 05/2015 
End 05/2019