Black Silicon Photovoltaics

Lead Research Organisation: University of Oxford
Department Name: Materials

Abstract

Urgent efforts are required to reduce the cost of renewable energy in order to tackle the worst effects of climate change. The fastest growing renewable energy technology is photovoltaics (PV), which will account for 30% of global power generation capacity in the coming decades. Silicon PV, which currently accounts for more than 90% of the market, is a proven technology where significant technological improvements will ensure further price reductions and increased deployment. Improvement in cell power conversion efficiency is a key driving factor in reducing the cost of solar energy, which this proposal aims to achieve by developing industrially-compatible optical enhancement, surface passivation and emitter formation techniques for silicon solar cells.
The methods developed as part of this project will be applied to the leading solar cell technologies based on mono- (c-Si) and multi-crystalline silicon (mc-Si). For c-Si, this is a rear junction (RJ) architecture also known as the interdigitated back contact cell, and for mc-Si, this is a front junction (FJ) architecture. To enhance the RJ cell technology, where the p-n junction is at the back of the cell and unaffected by the front surface texturing, the approach is to use a solution-based texturing technique that leads to optically black silicon surfaces. For the case of the FJ cell architecture, where formation of the p-n junction at the front surface alongside texturing has to be considered, gas-phase processes will be investigated. Upon developing effective antireflective surfaces for RJ and FJ solar cells the challenge becomes transferring the gain in photon capture to improvements in the efficiency of the cell. For this to take place the electrical properties of the surface must be studied, and methods developed to mitigate any electrical degradation due to the texturing processes. This project is uniquely positioned to address jointly the optical and electrical properties of the cells, and by doing so, aims to produce optimally textured surfaces that can be easily integrated into the manufacture of solar cells.
The project teams at Southampton and Oxford will draw on their close collaborations with the world-leading research institutes at Fraunhofer ISE, Germany, and UNSW, Australia. This will enable the demonstration of the proposed texturing technology on state-of-the-art silicon solar cells, as well as providing access to advanced techniques in characterisation and processing. These collaborations will also promote knowledge transfer to the UK research community. A core principle of this proposal is to contribute to improving industrial solar cell production. For this, two strategic industrial collaborations have been established. Firstly Tetreon Technologies, the leading UK manufacturer of industrial tools for solar cell production, will be closely involved in the project, with the aim of subsequently developing industrial equipment and processes for export to the global market. Secondly Trina Solar, one of the world's largest cell manufacturers and the industrial leader in high efficiency cells, will provide insight into the market and industry needs that this project aims to address. They will demonstrate successful processes in an industrial environment from cell to module manufacture. Through these collaborations this project will leverage cutting edge expertise in the complementary areas of surface passivation and light trapping to tackle the challenge of developing photovoltaic technology. The project will deliver substantially improved efficiencies for silicon based solar cells and modules and, through close collaboration with UK and international companies, will allow the research undertaken to be rapidly exploited in the form of new tools and processes for export to the global solar industry. Alongside the expertise within the team, its academic and industrial networks form an ideal basis for the innovative and impactful research programme.

Planned Impact

Lower cost, higher efficiency photovoltaic technologies will have a huge impact on the adoption and deployment of renewable energy sources worldwide as alternatives to the burning of fossil fuels. The transition to renewable energy is vital in order to avoid the worst effects of climate change and so developments in technology that can facilitate this transition will massively benefit society on a global scale. The availability of cheaper, more efficient solar cells, using the leading technology - silicon, with cell lifespans in excess of 25 years, will also help to reduce the UK's reliance on imported energy resources, providing greater energy security and resilience. This project directly targets these impacts by aiming to achieve step changes in power conversion efficiency for proven silicon photovoltaic technologies, using industrially-compatible processes.

Following huge growth over recent years, the global photovoltaics market is expected to be worth around US$350bn/year by 2020. Currently, silicon technologies account for over 90% of this market and this domination is not expected to change in the foreseeable future. With growth predicted to continue into the future, it is important to look for ways in which the UK can enter this market and exploit the commercial opportunities available. This project will provide UK companies with new advanced solar cell processing technologies that can be developed and integrated into UK made cell manufacturing tools for marketing to the global PV industry. This will have direct economic benefits in terms of boosting the UK's involvement in this key growing industry, leading to job creation, increased know-how, and enhanced prosperity. Furthermore, developments in characterisation techniques during the project could also yield considerable economic impact by opening up new markets for advanced characterisation systems made in the UK. Companies including Tetreon Technologies and Oxford Instruments will be actively involved in the project to ensure maximum UK based exploitation of the advances made in optical enhancement, surface passivation and emitter formation. They will also benefit from the industrial network established with one of the world's largest photovoltaic module manufacturers, Trina Solar.

The project is designed to achieve additional impact through the personal and professional development of the researchers involved. The experience gained through participating in a multi-institution project, collaborating with other researchers from the global PV academic community, as well as engineers from industry, will be invaluable for the career development of all involved. This will also contribute to transfer global knowledge and expertise in silicon PV to workers in the UK. The involvement of PhD students in the project will further enhance the impact of the project by providing opportunities for mentoring and training. The public engagement activities will be designed to inspire young people by educating them about the technical challenges involved in making better silicon solar cells and how the research on this project is tackling them. This will have a positive impact on society as a whole by encouraging more engagement in STEM subjects, leading to a workforce with the technical skills, knowledge and expertise required in today's technology-based economy.
 
Description UNSW 
Organisation University of New South Wales
Country Australia 
Sector Academic/University 
PI Contribution Phill Hamer (Research Fellow, Oxford) was made an Adjunct Lecturer at UNSW (effective 26/02/2016). Several joint research projects with Oxford and Warwick.
Collaborator Contribution Visits to the UK by leading academics. Several joint research projects with Oxford and Warwick.
Impact Phill Hamer (PDRA in Oxford) has been made an Adjunct Lecturer at UNSW (effective 26/02/2016). Many publications: DOIs: 10.1016/j.egypro.2016.07.070, 10.1007/s11708-016-0427-5, 10.1109/JPHOTOV.2017.2731778, 10.1002/solr.201700129, 10.3390/app8010010, 10.1063/1.5016854, 10.1002/pssa.201700293, 10.1002/pip.2928.
Start Year 2016