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PhD Students

Information for perspective PhD students

1) Exploring new Chemically Processed, Scalable and Stable Bi-based Inorganic Photovoltaic Films

 

This project is fully funded by the EPSRC UK Centre for Doctoral Training in Photovoltaics

 

Prof. Judith Driscoll, Dr. Robert Hoye and  Dr. Dan Credgington, Dept. of Materials Science and Physics, University of Cambridge, 01223-334468, jld35@cam.ac.uk

 

The photovoltaics field has been revolutionised by the emergence of lead-based hybrid perovskites. These materials are high quality semiconductors that can be deposited cheaply, from solution, at room temperature. However, the toxicity of lead and stability issues for these perovskites are driving a new search for more benign and stable alternatives.  We have been exploring BiOI as a possible lead-free contender material. To date, nanostructured BiOI has been explored in photovoltaic devices but has shown poor efficiencies (maximum 1.03%) as a result of low photocurrents,1–3 likely because of high interfacial recombination and/or poor transport properties. However, film growth has yet to be optimised for achieving high efficiency.

 

We have recently deposited BiOI thin films by chemical vapour transport (CVT) and have achieved excellent, phase pure material (fig. 1a and b). Measurements of the photoluminescence decay indicate a bulk lifetime of approximately 3 ns (fig 1c), which well exceeds the 1 ns lifetime threshold need to potentially achieved 10% efficient 4. The bandgap is measured to be 1.9 eV through absorption measurements and spectrally-resolved photoluminescence measurements. This is ideal for a top-cell absorber in a four-terminal tandem with silicon. We have also found BiOI to be phase-stable in air over a 200-day test period, which is two orders of magnitude better than the very popular methylammonium lead iodide perovskite.

 

In this project, systematic doping of BiOI with chalcogenides S and Se on the optical and electronic properties of the films will be studied. Literature suggests that substitutional doping of O with other chalcogenides results in a reduced bandgap, making it more suitable for a single-junction device.5  The aim is to form idealised microstructures in large area films, to tune the bandgap in the range of 1.9 - 1.5 eV and to maximise the charge-carrier mobility and minority-carrier lifetimes. A very wide range of state-of-the-art electrical and optical characterisation will be undertaken in collaboration with groups in Physics.

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Figure 1 a) X-ray diffractogram b) AFM micrograph of a BiOI film grown at 350°C by CVT on a fused silica substrate.
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Figure 2 time resolved PL decay of a BiOI film grown at 350°C by CVT on a fused silica substrate.

References:
1. K. Zhao, X. Zhang, and L. Zhang, Electrochem. commun., 2009, 11, 612–615;
2. K. Wang, F. Jia, Z. Zheng, and L. Zhang, Electrochem. commun., 2010, 12, 1764–1767; 
3. M. Fang, H. Jia, W. He, Y. Lei, L. Zhang, and Z. Zheng, Phys. Chem. Chem. Phys., 2015, 17, 13531–13538;
4. R. Jaramillo, M. J. Sher, B. K. Ofori-Okai, V. Steinmann, C. X. Yang, K. Hartman, K. A. Nelson, A. M. Lindenberg, R. G. Gordon, T. Buonassisi, Journal of Applied Physics, 119;
5. N. T. Hahn, A. J. E. Rettie, S. K. Beal, R. R. Fullon, and C. B. Mullins, J. Phys. Chem. C, 2012, 116, 24878–24886.

2) Development of REBCO Coated Conductors for Spherical Tokamak Fusion Reactors

 

This project is an EPSRC CASE studentship jointly with Tokamak Energy, Abington, UK.

 

Prof. Judith Driscoll, Dept. of Materials Science

 

Tokomak Energy is a private company building compact spherical Tokamaks for nuclear fusion power generation.  Critical to the success of these devices is the development of high field and temperature superconducting magnets made from commercial rare-earth barium copper oxide (REBCO) coated conductors. Fusion is an emerging market for these conductors, and improvements in their properties and manufacturing processes could drastically improve the performance and economics of future reactors. Factors such as critical current density in high magnetic fields, tape construction, resilience against neutron irradiation, and the speed and economy of manufacturing processes, may all be customised for this novel application.  The aim of this project will be to explore new ways in which REBCO coated conductors can be optimised for use in spherical Tokamaks, in order to accelerate the generation of commercial nuclear fusion reactors.

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Interesting visit to Seoul, Anseong, Hangzhou, Souzhou and Shanghai.

May 10, 2018

On her Far East visit, Prof. Driscoll first had a very interesting visit to our sponsor, Sunam and she also attended the Chinese Chemical Society Meeting.

APL Materials Conference, 10-12 April 2018

Apr 14, 2018

Successful APL Materials Conference on 'Interfaces in Energy Materials'

Kroll Prize

Apr 04, 2018

Judith is very pleased to be notified that she is to be the IOM3 Kroll Prize recipient in 2018, following in the footsteps of former notable recipients from her dept. (Prof. Fray and Best and Dr. Kumar).

Alumnus Donation to Driscoll group

Apr 04, 2018

We are very happy to report that Dr. Bill Welland has made a further donation to support the research in the Driscoll group. Having such unattributed funds is most welcome and needed. Hence, we are very grateful to Bill for his generosity and for his interest in our work.

Science Festival and Ice Cream

Mar 24, 2018

Judith, her group and other members of the Materials Science dept. take part in the annual Cambridge Science Festival. We are very grateful to Trinity College for sponsoring the event.

New funding from The Office of Naval Research Global

Mar 16, 2018

We are pleased to announce funding from The Office of Naval Research Global for a 3 yr. funded program for a postdoc to work on Nanostructured Metamaterials for High-Tc Superconductivity.

Prof. Driscoll attends the COST TO BE Spring meeting in San Feliu

Mar 12, 2018

She talks about the prospects and challenges of ALD for complex Oxides, with co-author Dr. Napari. The talk is based on a paper they have written for the '2018 Oxide Technology Roadmap'

Dr. Ady Suwardi passed his PhD thesis

Mar 09, 2018

Congratulations!

Dr. Mari Napari in COST Action HERALD Workshop

Mar 01, 2018

Dr. Mari Napari attended the COST Action HERALD Workshop in ICMAB Barcelona aimed for early career investigators (ECI) working in the field of ALD to create competitive proposals for joint, EU-funded research projects.

Prof. Driscoll visits Ras Al Khamiah, UAE

Feb 17, 2018

Prof. Driscoll attended the 10th meeting of IWAM. The meeting was in honour of Prof. Millie Dresselhaus who attended the meeting for many years.

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