Semiconductor nanocrystals for solar cells: Tuning shape, size and interface effects

Lead Research Organisation: University College London
Department Name: Chemistry


This project will be built on one of the major challenges in contemporary physical sciences, that is the efficient conversion of the Sun's light into electricity in solar cells. By combining the experiences of two leading material simulation groups in the UK and China, we will provide an atomistic understanding of the processes that occur under the influence of light in technologically important semiconducting materials, especially the II-VI chalcogenide semiconductors. Our approach will be to exploit our complementary expertise in modelling the electronic properties of nanostructured and defective crystalline systems, which we will apply to novel solar cell architectures using inorganic nanoparticles to absorb light - a highly topical area of interdisciplinary sciences at the heart of the stated research priorities of EPSRC. The primary focus of this project is on the simulation of real materials at length scales relevant to experimental analysis and photovoltaic device physics: bridging the gap between theory and experiment as well as the geographical divide between the UK and China. The project partners are Prof. Jingbo Li and Prof. Jian-Bai Xia from the Institute of Semiconductors, Chinese Academy of Sciences in Beijing, who are two world-leading experts in the simulation of semiconductor quantum dots. Together, we will address the fundamental physical processes occurring in a new class of nanostructure solar cells, where new electronic states introduced by the nanostructured materials can facilitate the utilisation of photons of sunlight that lie outside the range of traditional bulk heterojunction solar cells. In addition to providing the methodological advances required to describe these systems, we will address the optimal material combinations to enhance light to electricity conversion efficiencies in future solar cell devices. This project will utilise existing high performance computing infrastructures at both institutions, and all results will be directed into ongoing experimental work in both host countries. The successful outcome of the project promises substantial general impact in a key and highly relevant area of physical sciences, and the establishment of a strong material simulation collaboration between the UK and China in the fields of solar cells and computational materials science.

Planned Impact

This is an ambitious cross-cutting project, drawing from chemistry, physics and engineering, at the frontier of computational materials science and solar cell research. It takes advantage of both teams' complementary background experience in the application of electronic structure techniques within the solid-state chemistry and physics communities. It also addresses two key EPSRC priority research areas: Energy and Nanoscience, and fits directly in line with the European Union's stated Strategic Energy Technology Plan. Energy and materials innovation is of universal importance. This research constitutes a high impact body of work, which will be published in world-leading journals and be presented to a variety of international audiences and experts; we will take full advantage of our membership of various chemistry networks to ensure widespread dissemination of the results. The final breakthroughs will be summarised in a newsletter which will be widely distributed amongst academic and industrial researchers in the field. Simulations will be performed on a range of complex material systems using cutting-edge theoretical methods. The project will provide new information on important material systems and help focus and direct experimental efforts to the most beneficial areas to optimise current and discover new material properties; synergetic experimental groups have been indentified at both host institutions. To ensure a direct impact in the field of solar cells research, the results will be presented at a leading conference of the solar cell community (PVSC), which combines the leading academic and industrial researchers, investors and government officials from around the world. In relation to the UK economy, a number of solar cell start-up companies have emerged within the last few years (including Solar Press in London) and we will work with industry, wherever possible, to increase the exposure and demonstrate the excellent of UK photovoltaic research and development. It is essential that the UK secures its place at the centre of this emerging technology, whose importance is increasing exponentially each year: as the price of oil increases and reservoirs are further depleted, and carbon taxes are introduced, renewable energy alternatives, electricity from solar cells in particular, are becoming cost competitive. The energy payback time for commercialised thin film solar cells has recently been reduced to less than five years, with a guaranteed lifetime of twenty years; these limits will be further extended in third generation devices, e.g. in nano-particulate devices where substantially less active material is required. This project will have a tangible impact on the future of solar cells through fundamental materials research development and insights, which in its fruition should help both stimulate economic activity in the UK and provide a higher quality of life to society in general, due to the utilisation of a sustainable energy source. The challenging project goals related to novel solar cell architectures, combined with the acquisition of new research methodologies, and the training of two advanced researchers in state-of-the-art simulation techniques will serve to secure the position of both teams are the forefront of computational materials science research and ensure a strong global impact.


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Description This project has been successful in many respects. All stated objectives have been achieved. The major results include: (i) An improved multi-scale modelling approach has been developed that can treat nanostructured systems; (ii) The fundamental materials chemistry of transparent conducting systems that are used for photovoltaics has been extended to include knowledge of intrinsic limits on fundamental conductivity properties; (iii) A new software package for assessing the stability of photovoltaic materials has been written; (iv) The high temperature dynamical properties of metal oxides has been investigated; (v) The characterization of defects in low band gap semiconductors has been developed; (vi) UK-China collaboration on photovoltaic absorber materials (e.g. Cu2ZnSnS4) has been increased; (vii) A surprisingly wide variation in energy states in the transparent conducting material TiO2, shown to arise when only the crystal structure changes, has been discovered and explained; (viii) The difficulty in producing p-type samples of the wide-gap semiconductor GaN has been explained in terms of its defect properties.
Exploitation Route New research directions resulting from this project were used in the EPSRC Programme Grant "Energy Materials: Computational Solutions", EP/K016288/1. The software package, methodological developments, and insights into energetic and defect properties of materials used in photovoltaics will be of enormous benefit to researchers in the first instance, and to engineers and developers working to improve efficiencies in solar cell technology. Links with Chinese research groups will allow knowledge transfer between the UK and China.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Construction,Creative Economy,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections,Pharmaceuticals and Medical Biotechnology,Transport

Description We have developed modelling approaches and generated results on defect and transport properties of semiconductor and other oxide materials. Such approaches and results will be of use to the wider computational chemistry and physics community, as well as provide guides for experimental design. New research directions resulting from this project were used in a new EPSRC Programme Grant "Energy Materials: Computational Solutions", EP/K016288/1.
First Year Of Impact 2011
Sector Construction,Creative Economy,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport
Impact Types Societal,Economic