Students eligible for UK Research Council funding are welcome to apply to the 4-year (1 year MRes + 3 years PhD) fully funded projects summarised below. More information about funding eligibility can be found here.
The details for all projects available for 2017 start have now been uploaded. We strongly advise early applications.
Fully-Funded 4 Year CDT Projects - for UK applicants
Understanding and Enhancing the Stability of Sn based perovskites for all-perovskite tandem solar cells
Metal halide perovskites have emerged as an extremely promising photovoltaic (PV) technology due to their rapidly increasing power conversion efficiencies (PCEs) and low processing costs. Single junction perovskite devices have reached a certified 22% PCE, but the first commercial iterations of perovskite PVs will likely be as an “add-on” to silicon (Si) PV by making perovskite-on-silicon tandem cells with enhanced efficiency. However, an all-perovskite tandem cell could deliver lower fabrication costs, but requires band gaps that have not yet been realized. The highest efficiency tandem devices would require a rear cell with a band gap of 0.9 to 1.2 eV and a front cell with a band gap of 1.7 to 1.9 eV. Although materials such as FA0.83Cs0.17Pb(IxBr1-x)3 deliver appropriate band gaps for the front cell, Pb-based materials cannot be tuned to below 1.48 eV for the rear cell. Completely replacing Pb with Sn can shift the band gap to ~1.3eV (for MASnI3), but the tin-based materials are notoriously air-sensitive and difficult to process. We have very recently demonstrated a stable 15 % efficient perovskite solar cell based on a 1.2 eV bandgap FA0.75Cs0.25Pb0.5Sn0.5I3 absorber and integrated this into all perovskite tandem cells delivering over 20 % efficiency.
The key challenges now remaining are to: i) ensure that devices incorporating this new low band gap material will be stable enough to last for 25 years; ii) Push the efficiency of the combined tandem cell to above 25 and towards 30%, to deliver a thin film PV technology with far superior efficiency as compared to Si or GaAs. Within this PhD project, through a combination of electronic and spectroscopic fundamental investigations and through device construction and engineering, we will tackle these challenges and specifically aim to understand and control the mechanisms which are inducing degradation, and those responsible for influencing the electronic properties of the perovskite absorber layers.
For more information, contact Prof Henry Snaith: Henry.Snaith@physics.ox.ac.uk
NB: The MRes year will be undertaken at Imperial College, then the student will transfer to Oxford University for the DPhil
N-type organic thermoelectric materials
Of all energy produced, barely 40% are used to conduct actual work, large amounts of the remaining 60% are dissipated to the environment as waste heat. Recovering this wasted energy however is difficult, mainly due to a lack of suitable technologies. One technology particularly well suited for the recovery of low temperature (<250oC) waste heat are organic thermoelectric generators (OTEG). OTEG are based on organic thermoelectric materials, which when placed into a temperature gradient generate a voltage due to the Seebeck effect. Harnessing this voltage would allow to generate electricity form otherwise wasted energy. In contrast to brittle, often toxic inorganic thermoelectric materials, organic materials allow the fabrication of light-weight, large area conformal OTEG devices.
Thermoelectric generators require efficient n-type and p-type materials in order to achieve high efficiencies. Whereas several organic p-type materials have been very successfully introduced into OTEG, the development of n-type thermoelectric materials has proven more difficult and there is currently a lack of suitable n-type materials. This project aims to accelerate the development of n-type organic thermoelectric materials through (i) understanding doping in these materials; (ii) studying their charge transport; (iii) working closely with synthetic chemists to develop a new generation of high performing organic thermoelectric materials.
For more information, contact Dr Oliver Fenwick: firstname.lastname@example.org
NB: The MRes year will be undertaken at Imperial College, then the student will transfer to QMUL for the PhD.
Non-fullerene electron acceptors for solar cell applications
This project is part-funded by Eight19
This project has already been filled, so is no longer available to applicants.
Non-fullerene electron acceptors for use in organic solar cell applications have rapidly progressed in recent years to the point where they are now outperforming fullerenes in both device efficiency and stability. These molecules offer potential advantages over fullerenes, such as their ease of synthetic modification and facile purification, their potential for low cost, improved spectral absorption coverage and strength, and inherent morphological stability. This year, the McCulloch group has developed a series of rhodanine terminated small molecule acceptors with exceptional performance in combination with a range of electron-donating, hole transporting polymers, offering an attractive pathway for industrial development of solution processed bulk heterojunction organic photovoltaic devices. We demonstrated that an active layer with two electron acceptors can have a synergistic effect on device efficiency and even stability. Much fundamental work however remains to explore the origins of this increased performance. For example, the relationship between the energy levels in a three component active layer and the optimum energetic landscape is not fully understood. In addition, understanding the role that phase separation, molecular diffusion and partitioning, chi parameters and surface energy, plays in determining the complex microstructure is critical to develop new materials and processes. This studentship will explore new molecular design, and develop an understanding of the interrelationships between molecular structure, thin film microstructure and device performance.
We will design and synthesise a range of of calamitic shaped small molecules to be employed as electron acceptors in bulk heterojunction blends. The design strategy will focus on optimizing each tunable aspect of the molecular structure with respect to intrinsic properties such as molecular orbital energy levels, solubility and crystallinity, in addition to thin film heterojunction blend properties and absorption complementarity. The conjugated unit design strategy is based on discrete separation of electron rich and poor aromatic sections, drawing on a symmetric indacenodithiophene design template used in donor polymer synthesis. This has been an established and successful strategy to aid efficient materials optimisation and is a core area of expertise in the McCulloch group. A conjugated push-pull structure is achieved by combining this electron rich unit fluorene with an electron poor peripheral unit comprising benzothiadiazole and a terminal rhodanine. This molecular orbital hybridization reduces the bandgap, which helps to extend the absorption, to lower energies. Additionally, it provides control over the separation of the HOMO and LUMO electron density in the molecule thus influencing the molecular extinction coefficient, and the location for charge transfer.
The target of this studentship is to initially explore a range of molecular design modifications of the IDTBR acceptor unit, and the subsequent effects that these changes have on the performance of bulk heterojunction solar cell devices. The function of these acceptors will be evaluated in blends with donor polymers, including steady state and transient spectroscopic studies of electron and hole transfer in order to evaluate the impact of changes in materials design. The specific targets will be to minimise geminate recombination losses whilst maintaining a high acceptor LUMO level and therefore cell voltage.
For more information, contact Prof Iain McCulloch: email@example.com
Controlling magnetism in molecular thin films
Molecular materials have had an enormous impact on technology due to their unique optical, electronic and mechanical properties. Although it has attracted comparably less attention so far, their spin also offers huge potential in the field of e.g. low energy information technology or controllable optoelectronics. The low atomic number of the carbon-based framework enables extremely long spin lifetimes, which is a unique advantage compared to inorganic materials used traditionally. The basic building block of a spin valve, magnetic films, can be produced from molecular materials. However, although coupling strengths have increased by one order of magnitude over the last decade, they are still too low for room temperature operation. A change in the co-facial stacking distance in films of cobalt phthalocyanine (CoPc) has a dramatic effect on the magnetic coupling strength, leading to coercivity above liquid nitrogen temperatures. Excitingly, theoretical models based upon this result suggest that increasing the co-facial interaction further could lead to coercivity up to 400 K for fully cofacial stacks of CoPc. This is well above the temperature required for practical applications.
The aims of this project are to develop phthalocyanine analogues that can be deposited in cofacial stacks using highly controlled organic molecular beam deposition (OMBD). The use of OMBD is important because it allows exquisite control of the growth conditions, minimising defects and impurities which otherwise have a significant detrimental effect on magnetic properties, and allowing for the growth of the complex architectures required for spintronic devices. Similarly the phthalocyanine scaffold is important to promote axial interactions of the central metal atom, whilst isolating it from adjacent stacks, and offers a unique combination of optical, charge transport and magnetic properties.
The project will involve a close interaction between the Heutz and Heeney groups. Year 1-2 of the project will focus on the synthetic work, in particular further developing synthesis routes to separate isomers of Pc analogues vie traceless directors, and the dimeric materials. Years 2-4 will primarily focus on the growth and characterisation of thin films, utilising a variety of techniques to characterisation packing (GIXD, HR-TEM, AFM) and magnetic properties (SQUID). Feedback will guide the development of second and third generation Pcs.
For more information, contact Dr Sandrine Heutz: firstname.lastname@example.org
2D functional inks for flexible optoelectronics
This project is part-funded by Thomas Swan
Exfoliated 2d nanomaterials offer multiple beneficial physicochemical and functional properties in a format that can be prepared as an ink and printed to form flexible electronic devices. Graphene has attracted enormous interest but lacks a straightforward band gap, meaning it can only be conveniently used as a conductive material. Other 2d materials, such as Transition Metal Dichalcogenides (TMDs), offer a well-defined band gap, suitable for transistors, photodetectors, or emitters. By preparing and combining inks based on this palette of materials, device applications can be developed. To maximise the performance, the exfoliation process must be optimised, since the TMD properties depend on the degree of exfoliation and the lateral size of the layers, as well as their inherent structure. Thomas Swan & Co. are developing a range of functional inks based on 2d materials.
This project will explore the application of these inks to thin film electronics, linking the nature of the ink, through the deposition process, to transport properties and then device performance. The project will involve detailed characterisation using a range of advanced microscopy and scattering methods to determine the nature of the ink, establish protocols for patterned film (and hybrid film) deposition, and finally design/evaluate protoype devices. By iteration with the team at the company, new optimised materials will be developed, providing a rapid route to real world application.
Plan of Work:
Year 1: Characterisation of 2d nanomaterials dispersions provided by Thomas Swan Ltd. Optimisation of deposition protocols on plastic films, using physical and chemical means. Microstructural characterisation by SEM and (conductive) AFM. Optical/transport property determination.
Year 2: Determination of key performance controlling parameters (flake size, dispersant, deposition method, starting material type). Optimisation of ink systems to maximise transport performance. Development of functionalisation chemistry to modulate properties or improve film formation. Development of simple single component devices.
Year 3: Demonstration of TMD devices incorporating hybrid systems as electrodes. Consideration of other related opportunities, such as printable thick films for integrated electrochemical energy storage systems.
Year 4: Development of the most promising device embodiments and materials.
For more information, contact Prof Milo Shaffer: email@example.com
Spontaneous surface patterning for switchable photonics and metamaterials
Nano-structured surfaces exhibit unique optical, physical, mechanical and electronic properties. Conventional nanofabrication techniques, including electron and focused ion beam, nanoimprint and photolithography, are low throughput and costly for large area patterning. Bottom-up methods, including self-assembly and surface instabilities of soft materials offer an attractive alternative. Highly-ordered structures can be formed upon compression of a bi-(multi-) layer, due to the mismatch between the mechanical properties of a thin film and its compliant substrate.
This project will combine experiments and theory/modelling to fabricate novel optically active surfaces and evaluate their potential as photonic and metamaterial components, reaching sub-wavelength dimensions. Results will establish the governing conditions of this unbound and confined buckling instabilities and provide novel routes for nanotechnology with particular applications for light-management in passive optics (diffraction/phase gratings) and active devices, such as photovoltaics, detector and emitter technologies.
Switchable surfaces with tuneable wavelength (down to 10 nm), and amplitude (up to 60% λ) and patterning area up to 10 s.cm2 will be designed and fabricated, at an estimated £0.02/cm2 cost. These surfaces act as diffraction gratings, both in transmission and reflection, since the substrates can be optically transparent over a large spectral range. Multiaxial strain fields yield multi-frequency and orientation patterns, including Fresnel-type optics. The topographies can be permanently turned ‘on’, ‘off’ or oscillate dynamically. Spatially patterning of optically active features within a single support opens unique opportunities in very large scale integration (VLSI) and the ability to carry out a series of complex operations (diffraction, lensing, coupling, resonators etc). Wrinkling will be coupled with conventional mask-lithography and chemical patterning to laterally confine the wrinkling processes. The consequences are significant, as higher order patterns are achievable, including aspherical lenses and chiral surfaces. The exact window of applicability of this approach has not yet been established. We expect important ramifications for ‘structural colour’ with potential applications in coatings and paints. Further, the spatial control of the patterns (e.g. inducing a change in period of the pattern as a function of distance), allied with emitting or absorption bandwidth from (say) an organic material, can provide a means for spatially selecting (i.e. in detection/emission) the response. Structural techniques, well established from the radar community, could be realised at an optical level and suitable for a variety of optical sensing technologies.
The initial stages of the project (MRes) will include (a) attaining multiaxial patterning generated by well-defined strain fields, (b) elucidating the nature of wave superposition (using fresh or multiple pre-wrinkled surfaces), (c) defects and boundary conditions, including droplet seeding for determining interfacial profiles in bi/multilayers and demonstration of 10-100 nm wrinkles. This underpinning work naturally feeds into PhD areas that will include the optimisation of micro-nanopatterning over large areas and deployment into active devices. This will be accompanied by the full-field optical evaluation (i.e. RCS, diffractometry) of these surfaces across the visible, but also IR and UV spectrum, since all attainable by this patterning approach.
For more information, contact Dr Joao Cabral: firstname.lastname@example.org
Highly controlled synthesis of semiconducting and high dielectric polymers, using self-optimising flow-reactors
Polymerisation reactions undertaken in batch reactors are inherently difficult to control due to variability of such factors as temperature and concentration both throughout the reacting medium and over the duration of the reaction period. This typically leads to product polymer with poorly controlled average molecular weight and variable polydispersity – critical polymer parameters that have significant effects on processing and final materials properties. Polymer fractionation after polymerisation can be used to select a target molecular weight and reduce polydispersity, but it is a wasteful, expensive and time-consuming undertaking, and it is not generally feasible for high value electronic materials. New manufacturing methods capable of selectively synthesising polymers with desired properties – with minimal wastage – are urgently needed to overcome these problems.
Microreactors offer a complementary environment to conventional batch reactors, and have been shown to offer improved product selectivity for a wide range of chemical reactions, including polymerisations.
This project builds on significant expertise in microreactor technology at Imperial, encompassing both the design and fabrication of flow reactors and their subsequent application to areas such as sensing, small molecule synthesis, polymerisation and catalysis. This project is specifically focused on the development of methods for suppressing unwanted reaction side-products during polymerisation reactions to enable the direct synthesis of semiconducting and high dielectric insulating polymers with tightly specified physicochemical properties. This project aims to integrate a size-exclusion chromatography (SEC) instrument in-line with a microreactor to enable real-time monitoring of the average molecular weight and poly-dispersity of the polymerisation reactions. The effect of changes in variables (including, but not limited to, temperature, monomer concentration, ratio of monomers, catalyst concentration and solvent) will be investigated with in situ monitoring to determine the effect on electronic behaviour.
This project is well suited to a chemist or engineer wishing to gain hands-on experience of microreactors. According to the interests and background of the selected student, the project may focus on the development of novel microreactor hardware or the application of existing hardware to challenging chemistries that are hard to control using conventional flask chemistry. The opportunity exists for aspects of the project to be carried out collaboratively with AWE.
For more information, contact Prof John de Mello: email@example.com
Interrogating the dynamics of conjugated polymers using neutron scattering and molecular dynamics
This project is part-funded by Institut Laue Langevin Grenoble.
The electronic and optical properties of conjugated polymers depend critically upon the structures adopted by the polymer chains and the structural dynamics. Whilst the organisation of polymer chains in crystalline regions can be probed using diffraction techniques such as X-ray diffraction, most of the polymer in a thin film is composed of amorphous phases with no long-range order. Moreover, at room temperature the polymer chains are not frozen, and this strongly affects the electronic mechanisms such as charge carrier transport in electronic devices or charge separation in solar cells. Structure and dynamics can be simulated using atomistic molecular dynamics, but experimental probes of structure are required to validate the models. One of the most powerful probes of molecular structure and dynamics is neutron scattering (NS), where the interactions of neutrons with the polymer backbone and side chains can be measured as a function of temperature. Different techniques of NS allow to probe the structure and dynamics in different environments. Quasi-elastic neutron scattering (QENS) probes the polymer dynamics , inelastic neutron scattering is used to probe vibrational modes, while small angle neutron scattering (SANS) is used to probe the conformation of chains, for example, whether rigid or coiled. Despite of their potential, NS methods have seldom been applied to conjugated polymers partly because of the limited access to the hosting large scale facilities, and also because the interpretation of resulting data is complex.
This project builds on prior collaborative work between Imperial and the Institut Laue-Langevin, an international NS facility located in Grenoble, France. This work demonstrated that the backbone and side chain dynamics of polymers can be successfully determined using a combination of QENS and atomistic molecular dynamics.
This project will be extended to a number of new problems:
(1) the structure and dynamics of different conformations in films of a conjugated polymer that is known to display different phases. The aim here is to distinguish different conformations of a conjugated polymer in terms of the side chain and backbone dynamics. The beta conformation in poly(9,9) dioctylfluorene will be studied, which displays a planar conformation in comparison with a similar polyfluorene in which the beta conformer cannot form.
2) the effect of blending on the dynamics of two components in a “polymer:molecule” blend, in order to establish how molecular diffusion is influenced by the polymer environment. This question is relevant to the structural stability of blend films used in organic solar cells. A well characterised polymer such as P3HT blended with alternative molecular acceptors such as PCBM will be studied, as well as other fullerene adducts and oligomeric small acceptor molecules, and compare with device data;
(3) the dynamics of ion chelating conjugated polymers, which are being developed for applications as biosensors, in different (e.g. aqueous or organic solvent) environments. Here, deuterated side chains can be used to expose the dynamics and conformation of the side chains in different solvents and in the presence or absence of ions. This will help to clarify the mechanism of ion transport.
The student will design and conduct the NS experiments, characterise the material system, build a MD model of the system and analyse the results using MD simulations. The overall goal is to help establish design rules for the optimum conjugated polymer structure to maximize charge transport or charge separation.
For more information, please contact Prof Jenny Nelson: firstname.lastname@example.org
Innovative printed organic sensors
The project aims to develop innovative solution-processed (printed) organic sensors which enable to make fine discrimination of various external stimuli (gas, pressure, light, bio signal), ultimately facilitating the ubiquitous information system along with consumer electronics, bio-medical applications, smart buildings. This project will use a new cooperative stimulus-to-signal transducer (CSST) system comprising ionic liquid electrolytes as a stimulus receptor and pi-conjugated polymers as a signal deliver. This will form an interpenetrating network at a molecular level critical for a fast stimulus-to-signal transducing with high sensitivity, responsibility and reliability.
The project will focus on materials design/synthesis, materials/device characterisation, and platform technology development. The success of this project will offer a new class of materials for printed sensor applications, as well as will provide significant intellectual merit by unveiling fundamental device operational mechanism. This project will also take an advantage of conductive inks developed via solution processing (see the self-funded project “Developing conductive inks based on Si nanowires for printed electronics and sensors”, supervised by Dr Firat Güder). The conductive inks synthesized will be used for the fabrication of disposable diagnostic devices and electronic circuits, flexible circuit boards for wearable textile electronics.
For more information, contact Prof Ji-Seon Kim: email@example.com