Synergistic tailoring of flavins and quantum dots for solar cell applications

Lead Research Organisation: University of St Andrews
Department Name: Physics and Astronomy

Abstract

The development of renewable energy sources is an urgent problem and so large that many technologies will contribute. Solar photovoltaics can be expected to play a major role because of the abundance of solar energy, and the convenience of electricity as an energy source, but at present they contribute only a tiny fraction of the world's energy supply (e.g. ca. ~0.02% in the US). The major reason for the very limited uptake is that current solar cells are much more expensive than generating power from fossil fuels. Organic semiconductors have the potential to solve this problem by providing a route to much lower cost solar cells. Organic semiconductors are pi-conjugated molecules and polymers, that can be processed from solution via low cost/high volume deposition techniques such as spin-coating, roll-to-roll processing and ink-jet and screen printing. Conjugated polymers are an important class of organic semiconductor that can be used to make flexible thin film devices that are lightweight, highly portable, extremely fashionable and exceptionally marketable.A key barrier to the take-up of organic solar cells is that their efficiency is low (5-7% for solid state devices). This proposal describes a three-pronged approach, whereby each of these approaches has the potential to improve solar cell efficiency. The proposal aims to establish a new collaboration between Prof V. Rotello (UMass), Prof I.D.W. Samuel (St Andrews) and Dr G. Cooke (Glasgow). The synergy of our programme provides the potential for dramatic improvement in photovoltaic efficiency. The three approaches are summarised below:1. New flavin based electron acceptors will be produced with tailored energy levels and photophysical properties.2. New quantum dots will be produced with complementary energy levels to the flavin derivatives. The photovoltaic properties of patterned heterojunctions fabricated from these systems will be investigated.3. Moieties will be included into flavin and nanoparticle systems to facilitate self-assembly and enhanced charge separation. Prototype photovoltaic cells will be fabricated from these systems.

Planned Impact

The proposed research has significant potential for societal, commercial and academic impact. Renewable energy is a global issue and it is no overstatement to declare that our existence depends on a step-change in provision and attitude towards sustainable alternatives to fossil fuels. At present the use of solar photovoltaics is extremely limited because the cost is much higher than for electricity generated by burning fossil fuels, so the key challenge is to reduce the cost. The simple fabrication at low temperature of organic photovoltaic (OPV) devices provides a promising route to achieving this. However, the efficiency of these devices is at present too low and needs to improved to be at least 10%. We aim to use the complementary properties of colloidal quantum dots to enhance the performance of organic solar cells. In addition we will develop flavins as a new class of electron-transporting material and acceptor. There is a real shortage of solution-processable organic electron transport materials, so the flavins could see applications in related fields, such as transistors in addition to being used in more efficient solar cells. The combination of higher efficiency and simple manufacture of the solar cells we envisage would in the longer term (10-15 years) make them attractive for power generation - making an important contribution to solve the energy crisis. Applications in portable electronics and off-grid could be expected sooner (5-10 years). The UK and US are at the forefront of worldwide activity in organic electronics, and so in addition to the societal benefits outlined above, stands to benefit from such developments economically In addition the new materials approaches to be explored, combined with sophisticated measurements to understand the materials, will guide the UK and US academic communities towards even more efficient devices, which in turn will lead to societal and commercial benefits. Aspects of the proposed research are also likely to lead to materials insights and improvements relevant to other areas of organic electronics - as the control of energy levels and molecular ordering that we are proposing is relevant across this sector. After patenting any inventions arising from the project we are keen to present our results to companies as well as to other academics. In addition to presenting results at major academic meetings such as MRS we will also present at meetings with a more industrial bias and at UK meetings. We are excited about the potential for public engagement that this project will bring. The investigators and appointed researchers will capitalise on this through activities such as participation in science festivals, public lectures and school visits. These would include National Science Week, the Edinburgh International Science Festival and Lab in a Lorry. IDWS has first-hand experience of the commercialisation of inventions, together with professional institutional support in the protection of intellectual property (IP) and commercial exploitation of research. He has recent experience of both licensing and spin-out routes to commercialise several organic semiconductor inventions. This experience will be invaluable for recognising and implementing the most appropriate exploitation route for results arising from the project. The exploitation route will take account of the status of the technology and associated IP, the potential markets and the possible routes to those markets.
 
Description Novel solar cell materials were explored in this grant which also developed a new collaboration between the teams of Prof. Ifor Samuel (University of St Andrews), Prof. Graeme Cooke (University of Glasgow) and Prof. Vince Rotello (University of Massachusetts, Amherst). Organic solar cells typically consist of a donor and an acceptor. In this grant flavins were investigated as a new class of acceptor, and patterning techniques were also explored. the perfomrance of flavins was limited, but it was found that a sub-phthalocyanine could work well as an acceptor. An exciting unforeseen result was that we were able to use many of the acceptors to study the influence of driving force on electron transfer - a key process in the operation of an organic solar cell.
Exploitation Route They will guide solar cell researchers in the search for alternative acceptors. The effect of driving force work is important because it shows how much driving force is desirable which is very relevant to improving efficiency of organic solar cells.
Sectors Chemicals,Energy

 
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