DPhil Projects -Research Projects 2014-

Informal enquiries may be directed by email to the relevant potential supervisors. If project studentships are available, they are listed under the individual project.

Condensed Matter Physics is also associated with the following DPhil programmes:

DPhil Life Sciences Interface (DTC)
DPhil Systems Approaches in Biomedical Sciences (IDC)
DPhil Systems Biology (DTC)
DPhil Synthetic Biology (CDT)

Dr Sonia Antoranz Contera
Dr Arzhang Ardavan

Dr Richard Berry

Biological Rotary Molecular Motors

Nature DID invent the wheel, at least 3 times! The bacterial flagellar motor is 50 nanometres across, spins at over 100,000 r.p.m. driven by electric current, and propels swimming bacterial cells. ATP-synthase is even smaller, about 10 nm across, consists of two rotary motors coupled back-to-back, and generates most of the ATP - life's "energy currency" - in most living organisms. We are trying to discover how these living machines work. We develop and use a range of methods in light microscopy including ultra-fast particle tracking, digital holography, magnetic and optical tweezers and single-molecule fluorescence microscopy. Current projects in the lab: measurement of stepping rotation in flagellar motors, high-resolution single-molecule measurements of ATP-synthase in energized lipid bilyers, single-molecule fluorescence microscopy of protein exchange and dynamics in bacterial motility and chemotaxis, digital holography for tracking microscopic swimmers and flow fields, high-torque magnetic tweezers, building an artificial microscopic swimmer, templated assembly of flagellar rotors using DNA nanotechnology scaffolds (collaboration with Turberfield group). More...
Email Dr Richard Berry at: r [dot] berry1 [at] physics [dot] ox [dot] ac [dot] uk

Prof Stephen Blundell

Pulsed Magnetic Fields to Study Quantum Materials

The highest magnetic field in the UK is available at the Nicholas Kurti Pulsed Magnetic Field Laboratory in the Clarendon. The capacitor bank is currently being upgraded to a stored energy in excess of 2 MJ in order to push the maximum field to 70 tesla. The energy stored in the capacitors is used to drive a short pulse of very high current through the magnet coils, thereby producing a magnetic field profile which rises quickly to a very large maximum and then falls down to zero. Our pulsed-field facility allows some unique science to be performed: accessing the normal state of high-temperature superconductors and mapping out the topology of their Fermi surfaces; changing the energy level structure of a material and allowing excited states to be explored; driving quantum phase transitions; aligning spins and lifting the frustration in low- dimensional magnets; revealing hidden order or inducing new phases in magnetic or charge-ordered materials. The project involves experiments with pulsed magnetic fields to study a variety of new superconductors and novel magnetic systems and to make discoveries in the field of quantum matter.
Email Prof Blundell at: s [dot] blundell1 [at] physics [dot] ox [dot] ac [dot] uk.

Prof Andrew Boothroyd

Novel Electronic Order and Dynamics in Crystals

Systems of interacting electrons frequently exhibit subtle forms of order, examples being superconductivity and magnetism. In this project you will investigate electronic order and dynamics experimentally. Neutron and X-ray scattering will be the main techniques used, taking advantage of the new ISIS 2nd target station and the Diamond Light Source, plus other facilities in Europe. A willingness to travel is essential! Magnetic, transport and thermal measurements will be performed in the Clarendon Laboratory, and there is scope for theoretical modelling and numerical analysis. More...
Email Prof. Andrew Boothroyd at: a [dot] boothroyd1 [at] physics [dot] ox [dot] ac [dot] uk

Dr Yulin Chen

Topological Insulators - A New State of Quantum Matter

Figure 1: Surface conduction of topological insulators (A) The spin of electrons on the surface is correlated with their direction of motion (B) The lattice structure of Bi2Te3 and the predicted relativistic "Dirac cone" like electronic structure formed by the surface electrons. (C) The electronic structure measured by angle-resolved photoemission (Figure generated from data in Ref(1)) that confirmed the theoretical prediction and the topological nature of Bi2Te3.

Topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface (Fig. 1). The bulk of such materials is insulating but the surface can conduct electric current with well-defined spin texture. In addition, the relativistic energy-momentum relationship of electrons in these materials provides a great opportunity to study the physics of relativity in a condensed matter system with the velocity of massless particles about 200 times slower than the light speed in vacuum. The unique properties of the topological insulators make them great candidate for energy and technology applications.

Unlike other materials where the fragile surface states can be easily altered by details in the surface geometry and chemistry, topological insulators are predicted to have unusually robust surface states due to the protection of time-reversal symmetry. These unique states are protected against all time-reversal-invariant perturbations, such as scattering by non-magnetic impurities, crystalline defects, and distortion of the surface itself, and can lead to striking quantum phenomena such as quantum spin Hall effect, an image magnetic monopole induced by an electric charge, and Majorana fermions (whose anti-particle is itself) induced by proximity effect from a superconductor.

Extracting the electronic and structural properties of topological insulators is essential for both the understanding of the underlying physics and potential applications. As a direct method to study the electron band structures of solids, ARPES can yield rich information of the electronic bands of topological insulators, as demonstrated in our recent results on the realization of the large gap single Dirac cone topological insulator Bi2Te3(Ref 1), the insulating massive Dirac fermion state (Ref. 2), and a topological superconductor candidate (Ref.3). For more information, please visit http://www.topological-insulator.net

[1] Y. L. Chen, et. al., “Experimental Realization of a Three Dimensional Topological Insulator, Bi2Te3” Science, 325, 178 (2009)
[2] Y. L. Chen, et. al., “Massive Dirac Fermion on the Surface of a magnetically doped Topological Insulator” Science, 329, 659 (2010)
[3]. Y. L. Chen, et. al., “Single Dirac Cone Topological Surface State and Unusual Thermoelectric Property of
Compounds from a New Topological Insulator Family”
, Physical Review Letter, 105, 266401 (2010)

Email Dr Yulin Chen at: yulin [dot] chen [at] physics [dot] ox [dot] ac [dot] uk

Dr Amalia Coldea

Using High Magnetic Fields to Probe Unconventional States of Matter in Novel Superconductors and Topological Insulators

Understanding the behaviour of novel complex materials requires direct experimental access to their fundamental electronic properties. One such powerful method is to look directly at the quantum behaviour of electrons though quantum oscillations studies in high magnetic fields. A combination of highly sensitive experiments and predictions given by band structure calculations will aim to understand the newly discovered iron-based superconductors and the surface states of topological insulators. This knowledge will advance and help to predict future superconducting and multifunctional materials. The project will consist in using and developing highly sensitive tools to investigate micro-size single crystals and thin films. Thermodynamic and magnetotransport measurements will be performed in extreme conditions of high magnetic fields and low temperatures both in the Clarendon Laboratory and using high magnetic field facilities in Europe and the USA.
Email Dr Amalia Coldea at amalia [dot] coldea [at] physics [dot] ox [dot] ac [dot] uk

Dr Radu Coldea

Quantum Magnetism and Quantum Phase Transitions

We explore experimentally materials where quantum correlation effects between electrons are important and often lead to novel forms of electronic order or dynamics dominated by quantum effects. Of particular interest is the phenomenon of "quantum frustration", i.e. how quantum systems resolve competing interactions, this is explored in frustrated spin-, orbital- and charge-ordered systems. Another focus is "quantum criticality" when the transition temperature to spontaneous magnetic order can be suppressed by high magnetic fields all the way down to zero temperature, thus realizing a regime where all ~10^23 electron spins in the material fluctuate strongly, but in perfect unison, a new regime for quantum matter that is only now becoming accessible experimentally and we plan to measure directly the quantum spin fluctuations via neutron scattering. The DPhil project will involve a mix of thermodynamic measurements, xray and neutron scattering experiments, data analysis and modelling.
Email Dr Radu Coldea at: r [dot] coldea [at] physics [dot] ox [dot] ac [dot] uk

Prof John Gregg and Dr Alexy Karenowska

Magnon Spintronics

Magnons are the quasi-particles associated with electronic spin waves.
In certain magnetically ordered materials they are able to play the role of spin angular momentum carrying tokens which can be generated and transmitted over long distances (up to centimetres) and at high speed (many tens of kilometres per second).

A quartet of effects: spin-transfer torque, spin pumping, the spin-Hall effect, and the inverse spin-Hall effect permit the interconversion between magnon fluxes, spin currents, and charge currents. This functionality paves the way for magnon spintronics: the development of structures and devices which combine the rich physics and long-range spin angular momentum transfer capabilities of magnon systems with the established toolbox of conventional electron-based spintronics. However, the exploration of magnon spintronic systems is still very much in its infancy: improving our understanding of their underlying physics and its device applicability is essential if we are to exploit their potential to the full.

This project will combine investigations of fundamental aspects of magnon/spin/electron current interconversion in metallic and insulating magnetic systems with the development of new and exciting prototype magnon spintronic devices.

Email: Prof John Gregg and Dr Alexy Karenowska at:
j [dot] gregg1 [at] physics [dot] ox [dot] ac [dot] uk and A [dot] Karenowska [at] physics [dot] ox [dot] ac [dot] uk

Prof Laura Herz

Charge Generation Dynamics in Novel Materials for Solar Cells

Increasing world needs for electrical power have intensified research into materials suitable for cheap and efficient solar cells. Solution-processed semiconductors offer great benefits in this area, as they can be easily processed into devices allowing cheap production of large-scale solar panels. A number of exciting new materials systems have emerged, including dye-sensitized solar cells, organo-metal-halide cells, and all-organic molecular photovoltaics, each of which now offer power conversion efficiencies exceeding 10%. Surprisingly, many of the fundamental mechanisms underlying both the process of charge-separation from photoexcitation and subsequent motion to electrodes are still barely understood. During this project we will advance the efficiencies of photovoltaic systems by gaining an understanding of fundamental photon-to-charge conversion processes using a combination of ultra-fast optical techniques, e.g. photoluminescence upconversion and THz pump-probe spectroscopy. This project will be part of active collaboration with researchers working on solar cell fabrication within Oxford and the UK.

This project allows the exploration of physical phenomena in the increasingly popular area of solution-processed and nanostructured semiconductors, and offers a high degree of training in the elegant and versatile techniques of femtosecond optical spectroscopy.
Applications for this project can be submitted through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. Informal inquiries may be directed by email to Prof. Laura Herz at l [dot] herz [at] physics [dot] ox [dot] ac [dot] uk. Some useful information on funding for International Postgraduate Students may be found here.

Energy and Charge Transfer in Biomimetic Light-Harvesting Assemblies

Photosynthetic organisms use arrays of chlorophyll molecules to absorb sunlight and to transfer its energy to reaction centers, where it is converted into a charge gradient. These processes are remarkably fast and efficient, because the excited states are coherently delocalized over several chlorophyll units. For natural scientists striving to create new molecular light-harvesting materials for applications such as photovoltaics, the designs nature has invented for us are fantastic templates to learn from. This project will explore energy transfer within and between large porphyrin nanorings that directly mimic natural light-harvesting chlorophyl ring assemblies. By creating interfaces with electron-accepting molecules we aim to create light-harvesting layers that rival their natural counterparts in photon conversion efficiency. This project offers exciting possibilities for work in a new interdisciplinary area of research in collaboration with researchers at the Universities of Oxford (Harry Anderson) and Nottingham (Peter Beton).

This project allows the exploration of physical phenomena in the increasingly popular area of solution-processed and nanostructured semiconductors, and offers a high degree of training in the elegant and versatile techniques of femtosecond optical spectroscopy.

Applications for this project can be submitted through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. Informal inquiries may be directed by email to Prof. Laura Herz at l [dot] herz [at] physics [dot] ox [dot] ac [dot] uk. Some useful information on funding for International Postgraduate Students may be found here.

Optimizing Design, Morphology and Stability of Molecular Semiconductors for Next-Generation Photovoltaics -INDUSTRIAL CASE STUDENTSHIP JOINTLY WITH MERCK CHEMICALS (Fully funded for students with home fee status)-

Please find further information here.

Dr Thorsten Hesjedal

Thin Film Quantum Materials

We are interested in the growth and characterisation of epitaxial quantum materials such as topological insulators, novel magnetic spin systems, and spintronic devices. Our growth method of choice is molecular beam epitaxy (MBE) that enables the precise deposition of materials – one atomic layer at a time. Our dedicated MBE systems allow us to explore chalcogenides, transition metals and rare earths, as well as oxides.
Our group is located in the Clarendon Laboratory, as well as on the Rutherford Appleton Laboratory (RAL) site where we can be found in the state-of-the-art Research Complex at Harwell (RCaH). The RCaH is conveniently located next door to the UK’s new third generation synchrotron radiation source Diamond and the unique pulsed neutron and muon source ISIS - large scale facilities which we make regular use of for structural investigations and spectroscopy.
More ...
Email Dr Thorsten Hesjedal at: t [dot] hesjedal1 [at] physics [dot] ox [dot] ac [dot] uk

Dr Michael Johnston

Semiconductor Nanowire-Based Solar Cells

III-V nanowires, such as GaAs and InP nanowires, are high aspect ratio cylinders of crystalline inorganic semiconductor, typically with diameters of a few tens of nanometres and lengths of several microns. These novel nanomaterials offer outstanding potential as nano-components of future electronic and optoelectronic devices, and are especially promising candidates for the light absorbing and charge transporting elements of solar cells. Nanowire-based solar cells could be produced at a fraction of the cost of conventional solar cells, and offer the possibility of unprecedented energy conversion efficiencies. This project will involve the fabrication of novel nanowire-based solar cells and studying charge dynamics in these devices using terahertz spectroscopy.
Email Dr Michael Johnston at m [dot] johnston1 [at] physics [dot] ox [dot] ac [dot] uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

THz Conductivity of Graphene and Graphene-Like Materials

Two-dimensional nano-materials such as graphene are currently the platform for fascinating fundamental science and have the potential to become the building blocks for a new era of fast, low-cost electronics. These materials are already inspiring new device concepts for applications including photovoltaics, sensing, high-speed communications and computing. However at present the electronic properties of many of these new materials are poorly understood, which severely limits the realisation of these electronic devices. Furthermore, nano-materials have a particularly bright future in ultra-high (THz) frequency electronic devices, yet to date their properties have almost exclusively been studied only at low frequencies. This project will develop non-contact tools to measure the electronic properties of nano-materials to frequencies well in excess of the operating frequency of the fastest electronic devices available today.
Email Dr Michael Johnston at m [dot] johnston1 [at] physics [dot] ox [dot] ac [dot] uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

Terahertz Conductivity of Semiconductor Nanostructures and Devices

As semiconductor devices become faster and smaller it is increasingly important to understand the fundamental nature of charge carrier dynamics in these systems on a sub-picosecon d timescale. Conventional electronic transport and magneto-transport methods are incapable of measuring dynamics on such short time scales. However, "Optical Pump, Terahertz Probe Spectroscopy (OPTHzP)" is a new non-contact technique that allows such measurements to be performed with a femtosecond resolution, thereby revealing novel ultrafast physical processes. When fully understood such processes have the potential be utilised in future generations of electronic devices. This project will make use of the state-of-the-art OPTHzP systems in the Oxford Terahertz Photonics group to help understand charge dynamics in novel semiconducting nanostructures, including semicondutor nanowires (lower Figure), carbon nanotubes and porous InP.

Further Reading:
Our recent study of ultrafast conductivity in GaAs nanowires [more]
Our THz study of polymer field effect transistors [more]
A description of the carrier dynamics model that has been developed in the group [more]
Email Dr Michael Johnston at m [dot] johnston1 [at] physics [dot] ox [dot] ac [dot] uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

Controlling and Measuring the Polarisation State of Terahertz Photons: New Approaches to THz Spectroscopy and Imaging

In conventional optical spectroscopy only the intensity of light may be recorded, however in time-domain spectroscopy the electric fie ld of the light is recorded as a function of time giving complete amplitude and phase information of the light. This additional information allows the complete dielectric function of materials to be determined directly, thus allowing many physical properties of the matter to be extracted. The Oxford Terahertz group recently developed the first THz detector that can measure the full polarisation state of a THz pulse. In this project you will develop and exploit this technology into the areas of THz sepctroscopy and imaging. In particular this project will focus on studying the process of THz radiation emission from semiconductors and semiconductor nanostructures.

Further Reading:
Development of a three contact photoconductive detector of THz radiation [more]
Characterisation of the frequency-dependent birefringence of quartz [more]
Email Dr Michael Johnston at m [dot] johnston1 [at] physics [dot] ox [dot] ac [dot] uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

Prof Achillefs Kapanidis

Single Molecule Spectroscopy of Biomolecular Machines

Living cells contain thousands of molecular machines that process biomolecules. We study machines of gene expression, the path from "reading" genes on DNA to the synthesis of proteins. We seek to understand how machines work by observing individual molecules using cutting-edge single-molecule fluorescence methods (figure) which monitor nanometre distances in real-time and can "film" fascinating molecular movies of dynamic processes. Projects are multidisciplinary combining optics, spectroscopy, biochemistry, modelling and signal processing. More...
Email Dr Achillefs Kapanidis at: a [dot] kapanidis [at] physics [dot] ox [dot] ac [dot] uk

Dr Alexy Karenowska

Quantum Magnon Spintronics

Spintronics is the area of research dedicated to the study of how ‘spin’—the quantum mechanical currency of magnetism—can be used realize new types of information transport, storage, and processing system which surpass the capabilities of those currently found in our computers and other electronic devices.
The field of magnonics is the area of magnetics dedicated to the science of quasi-particles known as magnons. In certain magnetic systems, magnons are able to play the role of microscopic spin-carrying tokens which can be generated and transmitted over relatively long distances (up to centimetres) and at high speed (many tens of kilometres per second). Magnon spintronics, magnonics’ emerging sister discipline, is concerned with structures and devices which involve the passing of spin-information between magnons and electrons, the familiar workhorses of conventional electronics.
As appreciation of the interplay between magnonic and electronic spin-transport deepens, so excitement surrounding its possible contribution to next-generation information technology heightens. To date however, work in magnonics and magnon spintronics has focused on the study of room-temperature magnon and magnon/electron systems in the classical limit. As a result, the field of experimental quantum measurement and information processing has yet to explore what the magnonic theatre has to offer.
This project will involve working on the development of novel experiments for the investigation of magnonics and magnon spintronics at the quantum level. In particular, its goal will be to take some of the first steps towards accessing the new physics and technological opportunity at the interface between magnonic and magnon spintronic systems, and the techniques of contemporary quantum measurement and information processing.
Email Dr Alexy Karenowska at a [dot] karenowska [at] physics [dot] ox [dot] ac [dot] uk

Dr Karenowska has a further project, which is joint with Prof John Gregg. Please see above 'Prof John Gregg and Dr Alexy Karenowska.

Dr Peter Leek

Superconducting Circuit Quantum Computing

The last decade has seen remarkable progress in our ability to create and manipulate coherent quantum states in electric circuits built from superconductors and Josephson junctions. Coherence times have improved by 4 orders of magnitude over the last decade, and we are now at an exciting point in history at which we can realistically work towards scalable quantum computing. In our group we are investigating a range of promising solid state systems as building blocks of a future quantum computer, including superconducting qubits, and high quality electromagnetic and acoustic resonators, coupling them together using cavity QED. We are looking for a motivated student to join our team and work on the next generation of devices in which multiple qubits and resonators are coupled together to carry out elementary quantum computations.
Email Dr Peter Leek at: peter [dot] leek [at] physics [dot] ox [dot] ac [dot] uk

Prof Robin Nicholas

Quantum Transport in Graphene and Carbon Nanostructures

Carbon nanotubes and graphene (Nobel Prize 2010) are revolutionising the study of semiconductors and offer the potential for a new generation of devices which may supplant silicon. This project aims to study the electrical properties of graphene and carbon nanostructures in high magnetic fields where the electrical conduction is strongly influenced by quantum effects giving rise to phenomena such the Quantum Hall Effect and Coulomb Blockade. By studying nanostructures which are typically only a few nanometers in size the energy levels and transport can be controlled and modified to create new properties and behaviour. The structures to be studied will be made using a recently installed next generation electron beam lithography system capable of writing features down to a size of 20nm and it is planned to experiment with combining these with carbon nanotubes also. More...
Email Prof Robin Nicholas at r [dot] nicholas1 [at] physics [dot] ox [dot] ac [dot] uk

Carbon Based PhotoVoltaic Devices

Finding new ways to produce Photovoltaic (PV) cells with high efficiencies and novel manufacturing techniques is a challenge for semiconductor physics. This project will explore the use of graphite, carbon nanotubes and polymer semiconductors to produce new structures which can act as PV devices with responses in both the visible and infrared part of the spectrum. The project will combine optical spectroscopy of carbon nanotube/polymer nanostructures with studies of electrical properties and fabrication techniques.

The experiments will use techniques such as PhotoLuminescence Excitation (PLE) spectroscopy to study the transfer of energy and charge through different components of the cells and infrared spectroscopy to examine the behaviour of transparent conducting layers such as graphene and nanotubes. These techniques will be combined with electroluminescence and photoresponse to evaluate the potential efficiency of the devices. More...
Email Prof Robin Nicholas at r [dot] nicholas1 [at] physics [dot] ox [dot] ac [dot] uk

Prof Paolo Radaelli

Novel Magnetic Materials for Data Storage: Multiferroics and Magnetoelectrics

Fig. 1: Magneto-orbital helices in CaMn7O12. This extraordinary texture of spins and orbitals is responsible for the highest multiferroic polarization ever observed. See N. Perks et al., Nature Communications 3 , 1277 (2012)

Multiferroic and magnetoelectric materials respond to the application of both electric and magnetic fields. This affords a much greater degree of control than it is possible with present magnetic media, so that these materials could form the basis for the next generation of information storage and reading devices. Unfortunately, most known multiferroic and magnetoelectric materials only work below room temperature. A recent breakthrough was the discovery of the largest magnetically induced polarization reported to date in the calcium manganese oxide CaMn7O12 (Fig 1), and the explanation of this phenomenon in terms of a new concept we introduced, the ferroaxial coupling. This project will extend this work on new materials families, as part of an EPSRC-funded effort to apply new concepts to the rational design and understanding of functional multiferroics and magnetoelectrics. In our group, we employ a variety of state-of-the-art experimental and theoretical techniques. We grow our own multiferroic crystals, characterize them in the lab with magnetic, optical and electrical measurements and study their microscopic crystal and magnetic structures using resonant and non-resonant X-ray diffraction (mainly at the Diamond Light Source) and a variety of neutron scattering techniques, including magnetic diffraction (mainly at the ISIS facility) and spherical neutron polarimetry (at the Institut Laue-Langevin in Grenoble). Theoretical methods, such as those based on the Density Functional Theory, are employed to model the static and dynamic properties of these systems, both at low temperatures and at room temperature (the theory activity is carried out in collaboration with the Materials Modeling Laboratory, Oxford Department of Materials). This DPhil project will involve a combination of all these techniques, chosen to suit the talents of the individual students, with a particular emphasis on the discovery, characterization and modeling of new magnetoelectric materials.

Email Prof Paolo G. Radaelli at p [dot] g [dot] radaelli [at] physics [dot] ox [dot] ac [dot] uk .

Dr Moritz Riede

Organic Solar Cells Based on Small Molecules

The first wave of products using organic semiconductors has very successfully entered the market: organic light emitting diodes (OLED) are used in the displays of many mobile phones, featuring brilliant colours etc.. Key to their success is the use of molecular doping, i.e. the modification of a semiconductor's properties by a controlled addition of "impurities". Although much less used in organic solar cells, the same concept of molecular doping can be applied here with similar benefits, enabling a cheap, efficient, light-weight and flexible renewable energy source.
This DPhil project aims at making and better understanding organic solar cells based on small molecules and the concept of molecular doping. The devices will be made by vacuum processing, allowing a high control of the composition and thickness of individual layers, and characterised by a range of experimental techniques. Important questions to be addressed are how the microstructure in thin film influences the optoelectronic properties of the solar cells, what fundamental limiting processes there are, and how any losses in the energy conversion can be reduced. As organic solar cells are only one possible application of organic semiconductors and molecular doping is considered as enabling technology for the exciting and highly interdisciplinary field of organic electronics, this work will be carried out in collaboration with other researchers at the Clarendon Laboratory and beyond.

Email Dr Moritz Riede at moritz [dot] riede [at] physics [dot] ox [dot] ac [dot] uk.

Fundamentals of Molecular Doping of Organic Semiconductors

A key component for making displays consisting of organic light emitting diodes (OLEDs) a reality was the development of molecular doping. Molecular p- and n- doping has similar advantages as p- and n-doping in inorganic semiconductors, i.e. raising the number of free charge carriers, controlling the Fermi level, increasing the conductivity, and obtaining quasi-ohmic contacts at interfaces. It is today exploited on a commercial level in the electron and hole transport layers in OLEDs. However, principles as basic as how free charges are generated in organic semiconductors with their low dielectric constant are highly debated. This makes the development of novel dopants that show more efficient doping, less diffusivity, and better long term stability challenging. Additionally, most p- and n-dopants have been developed for transport layers in OLEDs. On the one hand, OLEDs have different requirements on the dopants than organic solar cells and other organic electronic devices. On the other hand, work using p- and n-dopants not in transport layers, but as part of the optoelectronic active layers, e.g. in p-n homojunctions analogous to inorganic semiconductors, has only just started, opening up a wide field of research and possible applications. Molecular doping is considered by many an enabling technology for OE and may have similar impact as the development of doping for inorganic semiconductors. This DPhil project aims at exploring the fundamentals of molecular doping and find creative ways to use molecular doping to make organic electronics better.

Email Dr Moritz Riede at moritz [dot] riede [at] physics [dot] ox [dot] ac [dot] uk.

Prof John Ryan

Dr Henry Snaith

Perovskite Solar Cells

(Lee et al. Science 2012)

In the last 12 months we have had an unexpected breakthrough in the field
of emerging photovoltaics with the realization of over 15% efficient solid-state hybrid solar
cells based on organometal halide perovskite absorbers. These solar cells are fabricated from extremely inexpensive material and are remarkably efficient, with prospects for significant improvement in the next few years, setting them apart from other emerging PV technologies. We have DPhil projects centred around perovskite solar cells, with activity ranging from synthesising new perovskite absorbers, with a goal to understand the influence of structure and composition upon charge generation and electron-hole lifetime, through to thin film processing, device fabrication and advanced spectroscopy.

Email Dr Henry Snaith at h [dot] snaith1 [at] physics [dot] ox [dot] ac [dot] uk

Prof Robert Taylor

Coupled Cavities and Photonic Molecules

(i) I am currently collaborating with Hitachi Research Laboratories in Cambridge, as well as with the Universities of Cambridge, Sheffield and Imperial College London on several projects related to semiconductor quantum dots. A project that I am keen to have a research student to work on involves trying to achieve coupling between photonic crystal cavities in InAs quantum dot-based systems. The project will centre on the development of indexed quantum dots in a photonic bandgap structures consisting of two or more optical cavities. Time-resolved and coherent control techniques are employed.
This project will include a CASE STUDENTSHIP award in cooperation with Hitachi.

See my web page for details.

Email Prof. Robert A. Taylor at: r [dot] taylor1 [at] physics [dot] ox [dot] ac [dot] uk

Probing Energy Transfer in Organic Molecules Using Microcavity Spectroscopy

(ii) A second project involves working on cavities made by Dr. Jason Smith here in Oxford using a focused ion beam at the Department of Materials to try and produce coupling between cavity modes and large molecules. This work is funded as part of a grant awarded by the Oxford Martin School.

See my web page for details.

Email Prof. Robert A. Taylor at: r [dot] taylor1 [at] physics [dot] ox [dot] ac [dot] uk

Dr Stephen Tucker

Prof Andrew Turberfield

DNA Nanostructures

Structures built from synthetic DNA, such as the tetrahedron shown, can be used as templates to create molecular devices with nanometre precision. The new science of synthetic molecular systems has applications from physics and computer science to structural biology and medicine. Current projects include: the physics of self-assembly; applications of methods of computer science to the design and control of self-assembly; design and fabrication of synthetic molecular motors, including single-molecule measurements and programmable automata; autonomous molecular machinery for chemical synthesis; molecular computation; DNA-templated protein arrays for molecular structure determination; hybrid DNA-protein structures to investigate the biophysics of motor proteins; nanostructures as sensors and intelligent drug delivery vehicles. More...
Email Prof Andrew Turberfield at: a [dot] turberfield [at] physics [dot] ox [dot] ac [dot] uk