In Pressurised Water Reactors, the reactor pressure vessel (RPV) is considered a life limiting component due to the degradation of its mechanical properties. Nano-scale Cu-enriched precipitates are known to cause embrittlement in the form of increases in hardness and the ductile-to-brittle transition temperature. The effect of irradiation on the RPV is the dominant contributor to this embrittlement. This is due to the increased mobility of Cu from the high number of vacancies, and the matrix damage providing many heterogeneous nucleation sites. However, there are also thermal effects which may be difficult to separate from the irradiation effects. To understand the contribution of the long term thermal ageing to RPV embrittlement a series of weld and plate materials containing systematic variations of Ni and Cu has been thermally aged for times up to 100,000 hrs at 330 degrees C, 365 degrees C and 405 degrees C. Microstructural characterisation using Atom Probe Tomography has been performed. Complimentary Monte-Carlo simulations have been used to investigate the early stages of formation of Cu-enriched precipitates. Thermal ageing produces a high number density of nano-scale Cu-enriched precipitates. These nanometre precipitates have a Ni-Mn-Si rich interface which was found to be wider with increased precipitate size, lower ageing temperature and higher bulk Ni content. This interface reduces the interfacial energy of the Cu-enriched precipitates through a combination of the minimising of unfavourable Fe-Cu bonds and reduction in lattice strain. The matrix Cu levels after ageing for 90,000 - 100,000 hrs were found to be around 0.06 - 0.07 at.%, close to the expected solubility limits for Cu in Fe. The Fe content of the precipitates has been characterised and found to be higher at lower ageing temperature and for smaller precipitate sizes. Cu precipitation and solute segregation at dislocations were observed, particularly in the SG steels aged at higher temperatures where the supersaturation is lowest. Movies were produced from the Kinetic Monte-Carlo modelling (see accompanying DVD) and along with other analyses indicated that sub-critical Ni and Mn clusters may be active in the formation of Cu-enriched precipitates. This mechanism appears to occur in both the high and low Ni steels. Thus, the higher number density of larger precipitates observed with increased bulk Ni content is thought to be a consequence of the greater number of sub-critical Ni-Mn clusters providing more nucleation sites. A small number of grain boundaries were examined. Segregation of many solute species to them was observed, which is thought to result from a multi-element co-segregation process. Ni-Mn-Si precipitates were observed at grain boundaries and dislocations in the high Ni steels with high and low Cu levels. These are consistent with similar phases in found in irradiated high Ni steels. In the high Cu steels these particles were much larger and associated with Cu-enriched precipitates.

This thesis reports studies done on single-walled carbon nanotubes (SWNTs) using optical spectroscopy as the primary investigative technique. It focuses on advances in sample preparation which have been made possible through improvements to the method of photo-luminescence excitation (PLE) mapping of nanotubes. An introduction to the field and some theoretical models are presented initially to provide a background to the experimental chapters which follow. A description of the standard procedure for sample preparation in aqueous surfactants is then followed by a detailed introduction to PLE mapping, including modeling of SWNT spectra. The next chapter discusses improvements to the sample preparation method by using organic polymer solutions instead of aqueous surfactants for suspending the nanotubes. The results show reductions in the distribution of SWNT species which are solubilised, leading to significant improvements in the resolution of the optical absorbance spectra and an increased photoluminescence yield. Two experiments which were performed on the novel polymer-SWNT systems are then described. The first shows (via PLE mapping) that energy is transfered to the SWNTs when the polymer is photo-excited. The possible mechanisms behind this, as well as the implications for using carbon nanotubes as an additive in polymer photovoltaics, are discussed. The second experiment details a recent magneto-PL study of SWNTs embedded in films produced from the polymer solutions. Here, the improved optical signatures and absence of strain at low temperatures have revealed a previously unseen high field intensity dependence. The behavior has been explained by the magnetic field induced mixing of the excitonic states.

Spin properties of donor impurities in silicon have been investigated by electron spin resonance (ESR) techniques for more than sixty years. These studies gave us a contribution towards understanding some of the physics of doped semiconductor materials in general, which is the platform for much of our current technology. Despite the fact that donor electron and nuclear spins have been researched for so long, ESR studies of their properties are still giving us interesting insights. With the introduction of the concept of quantum information in the 1980s, some properties of donor spins in silicon, that were known from the fifties (such as long relaxations), have been reinterpreted for their potential application in this field. Since then, incredible experimental results have been achieved with magnetic resonance control, including manipulation and read-out of individual spins. However, some open questions are still to be answered before the realisation of a spin-based silicon quantum architecture will be achieved. Currently, ESR studies still contribute to help answering some of those questions. In this thesis, we demonstrate electrical and optical methods for donor charge state manipulation measured by ESR. Recent experiments have demonstrated that coherence time of nuclear spins may be enhanced by manipulating the state of donors from neutral to singly charged. We investigate electric field ionisation/neutralisation of arsenic donors in a silicon SOI device measured by ESR. Below ionisation threshold, we also measure the hyperfine Stark shift of arsenic donors spins in silicon. These results have, for instance, implications on how fast individual addressability of donor spins may be achieved in certain quantum computer architectures. Here, we also study optical-driven charge state manipulation of selenium impurities in silicon. Selenium has two additional electrons when it replaces an atom in the silicon crystal (i.e. double donor). The electronic properties of singly-ionised selenium make it potentially advantageous as spin qubit, compared to the more commonly studied group-V donors. For instance, we find here that the electron spin relaxation and coherence times of selenium are up to two orders of magnitude longer than phosphorus at the same temperature. Finally, we demonstrate that it is possible to bring selenium impurity in singly-charged state and subsequently re-neutralise them leaving a potential long-lived ⁷⁷Se nuclear spin.

The structural chemistry and magnetic properties of compounds isostructural with La₁₈Li₈Rh₅O₃₉ have been studied. In this cubic structure (space group Pm^{^_}<sub style='position: relative; left: -.5em;'>3</sub>n), [111] chains of alternating RhO₆ octahedra (2a, 8e sites) and LiO₆ trigonal prisms (16i site) occupy channels within a La-O framework. In order to study the consequences of both reducing the dimensions of the channels and introducing paramagnetic cations into both the framework and the polyhedral chains, compositions in the series Nd₁₈Li₈Rh_5-xFe_xO₃₉ (1 &le; x &le; 4) have been synthesised and characterised by magnetometry, neutron diffraction and Mössbauer spectroscopy. Iron preferentially occupies the 2a site as low-spin Fe(IV) and the larger 8e site as high-spin Fe(III). Compositions having x > 1 show spin-glass-like behaviour below ~5 K. The behaviour of this series of compositions has been compared with that of the known series La₁₈Li₈Rh_5-xFe_xO₃₉. In order to facilitate this comparison, the structure of La₁₈Li₈Fe₅O₃₉ has been fully characterised by both neutron diffraction and EXAFS. The use of both techniques has revealed differences between the mean and local environments of iron. In order to explore and extend the range and combinations of elements that can be accommodated in this structure, the Ti-containing compounds Ln₁₈Li₈M₄TiO₃₉ (Ln=La,Nd,Pr,Sm; M=Rh,Fe,Co) have been synthesised. Nd₁₈Li₈Fe₄TiO₃₉ was selected for a detailed study by magnetometry, neutron diffraction, Mössbauer spectroscopy and XANES. Cations were found to be stabilised in unusual oxidation states and disordered over three sites of the Nd₁₈Li₈Fe₄TiO₃₉ polyhedral chains. The 8e site is occupied by high-spin Fe³⁺, Ti³⁺ and Li⁺ in a ratio of 76:20:4; the 2a site by low-spin Fe⁴⁺ and Ti⁴⁺ in a ratio of 79:21 and the trigonal-prismatic 16i site by Li⁺ and Fe³⁺ in a ratio of 98:2. Nd₁₈Li₈Fe₄TiO₃₉ undergoes a transition to a spin-glass state at 4.25(5) K, whereas La₁₈Li₈Fe₄TiO₃₉ revealed a different type of magnetic transition at ~8 K. The nature of this transition is not yet clear. Monophasic samples could not be prepared in the Nd/Rh system and cation vacancies were found in Nd/Co. No pure samples of Sm-containing compositions could be prepared, while the only Pr composition which was obtained pure, according to X-ray diffraction, Pr₁₈Li₈Co₄TiO ₃₉ shows the similar magnetic properties to Pr₁₈Li₈Co₃TiO₃₉. The compositions Ln₁₈Li₈M₃ M'O₃₉ (Ln=La,Nd,Pr,Sm; M,M'=Fe,Co,Ti) with 25% of the 8e sites vacant have been investigated. The Co-containing compositions Nd₁₈Li₈Co₃FeO_39-y, Nd₁₈Li₈CoFe₃O_39-y and Nd₁₈Li₈Co₃TiO_39-y were characterised by neutron diffraction. Cation vacancies on the 8e sites were found to coexist with anion vacancies around the 2a sites. The remaining octahedral sites are occupied by a disordered arrangement of transition-metal cations. The trigonal-prismatic sites are fully occupied by Li except in the case of Nd₁₈Li₈CoFe₃O_39-y where some Fe is present, as confirmed by Mössbauer spectral data. Antiferromagnetic interactions are present on the Nd sublattice in each composition, but a spin glass forms below 5 K when a high concentration of spins is also present on the octahedral sites. The magnetic character of the Ln cations plays an important role in determining the properties of these compounds. Long-range magnetic order of the transition-metal cations was not observed in any compositions. Although this might be partly attributable to the cation disorder in the polyhedral chains, the apparent antiferromagnetic behaviour of Nd-containing compositions in which the transition metals have a low magnetic moment, e.g. Nd₁₈Li₈Co₃TiO_39-y, and the marked contrast between certain La and Nd compositions in which the transition metal content is the same, e.g. Nd₁₈Li₈Fe₄TiO₃₉ and La₁₈Li₈Fe₄TiO₃₉, suggests that the Ln sublattice is fully involved in determining the magnetic behaviour.

Através do uso de reagentes ambientalmente corretos, foram desenvolvidos métodos mais simples que os tradicionais para obtenção de diversos tipos de nanopartículas de magnetita (MagNP) funcionalizadas. Em todos os casos foi confirmado um comportamento superparamagnético consistente com a presença de monodomínios magnéticos de Fe3O4, com diâmetros médios de partícula inferiores a 100 nm, além de histerese nula acima de 280 K, Tb=90K em H=500 Oe e magnetização de saturação em torno de 90 emu g-1. Os métodos de síntese das MagNP foram conduzidos em solventes derivados do biodiesel de soja/mamona, em substituição ao insumos importados, permitindo uma redução significativa nos custos de produção desse tipo de nanomaterial, e viabilizando sua produção em larga escala. Os nanomateriais foram voltados inicialmente para captura, separação e reciclagem de insumos e produtos químicos, incluindo poluentes, catalisadores e enzimas, utilizando ímãs externos. Os procedimentos desenvolvidos proporcionaram uma alternativa verde para os processos convencionais que fazem uso extensivo de solventes, geram muito descarte, e utilizam processos com alta demanda de energia, como centrifugação, extração por solventes e filtração sob altas pressões. As MagNP foram especialmente projetadas para serem dispersas em diversos meios polares e apolares, de acordo com o tipo de funcionalização química na superfície, utilizando principalmente moléculas orgânicas anfifílicas capazes de se ligar na superfície do Fe3O4 por meio de grupos polares, e com matrizes carbonáceas por meio de interações hidrofóbicas. Dessa forma foram gerados novos nanomateriais superparamagnéticos incorporando diversos tipos de matrizes que foram testadas para a remoção de óleo e de compostos orgânicos responsáveis por odores e cores indesejadas em efluentes industriais, bem como para a captura, transporte, recuperação, análise de espécies metálicas ou orgânicas. Foram testadas janelas ópticas e displays nos quais a intensidade de luz transmitida ou refletida pode ser modulada com ímãs externos. O projeto, financiado pela PETROBRÁS contemplou ainda outras aplicações sigilosas, que foram omitidas desta tese. Seu andamento abriu uma importante janela em prol da sustentabilidade, levando ao início do desenvolvimento no Laboratório, da nanomagneto-hidrometalurgia verde para obtenção e reciclagem de metais estratégicos, e de trabalhos de despoluição magnética de ambientes contaminados. / New routes for low cost production of functionalized magnetic nanoparticles (MagNP) have been pursued in this Thesis, by employing environmentally compatible chemicals and resources. The nanomaterials exhibited typical superparamagnetic behavior consistent with the presence of magnetic monodomains, revealing no hysteresis above 280 K, Tb = 90 K at H = 500 Oe, and saturation magnetization as high as 90 emu g-1. The synthetic procedures were carried out using biocompatible solvents derived from biodiesel of soybean and Brazilian mamona seeds, leading to substantial reduction of cost for large-scale production. The superparamagnetic nanoparticles were initially designed for capturing, transporting and recycling chemicals or drugs, including pollutants, catalysts and enzymes, using external magnets. They provide a green alternative strategy for conventional processes that make extensive use of solvents, generate too much waste, and proceeds through highly energetic demanding steps such as centrifugation, solvent extraction and high-pressure filtration. In our work, the MagNPs were appropriately modified for working in polar and non-polar media, employing for instance, amphiphilic species for interacting with Fe3O4 using the available polar groups, and also with carbon surfaces by means of hydrophobic interactions. Accordingly, new superparamagnetic nanomaterials incorporating several types of materials carbon based. It was observed that the carbon materials containing 15 to 20% of magnetic nanoparticles could be completely removed from the media with the use of a magnet. In this way, the functionalized superparamagnetic nanoparticles proved useful for the removal of oil spills and of organic pollutants from industrial processing water, as well as for the capture, removal and recovery of metallic elements and organic species from the effluents. In addition, as a proof of concept, smart windows and displays were elaborated based on the modulation of the transmitted or reflected light by the external magnet. This work was sponsored by PETROBRÁS, and also covered missing, non-authorized aspects involved in two patent applications. Finally, an important consequence to be mentioned is the contribution of this project for launching new chemical routes towards sustainability, such as the development in this Laboratory, of green, magnetic nano-hydrometalurgy for processing and recycling strategic metals, and of the magnetic remediation of polluted environments using the functionalized nanomaterials.

In this thesis morphologies, coarsening mechanisms and kinetics are examined in a systematic way, when phase separation and subsequent microstructural coarsening is modelled using deterministic mean field and stochastic Monte Carlo methods. For the mean field approach a microscopic diffusion equation due to Khachaturyan is employed, and a variation of it with an environment dependent mobility. Monte Carlo simulations are carried out with vacancy and Kawasaki dynamics, and a residence time algorithm is applied in the vacancy case. In mean field models microstructural evolution results from a direct minimization of a free energy functional, and the mechanism of atomic diffusion does not appear explicitly. In Monte Carlo models, changes in site occupancies are effected by direct exchanges of neighbouring atoms (Kawasaki dynamics), or through vacancy motion. In this thesis the correspondence between mean field and Monte Carlo models in describing phase transformations in binary alloys is examined. Several examples of cases in which these differences between deterministic and stochastic models affect the phase transformation are given, and the underlying differences are analyzed. It is also investigated how the choice of diffusion mechanism in the Monte Carlo model affects the microstructural evolution. Most Monte Carlo studies have been carried out with Kawasaki dynamics, although in real metals such direct exchanges are very unlikely to occur. It will be shown how the vacancy diffusion mechanism produces a variety of coarsening mechanisms over a range of temperatures, which the Kawasaki dynamics fails to capture. Consequently, kinetics and resulting morphologies, especially at low temperatures, are affected. Finally, the question of physicality of time scales in mean field and Monte Carlo models is addressed. Often a linear dependence between Monte Carlo time and real physical time is assumed, although there is no rigorous justifcation for this. In mean field models, time is defined through the atomic mobility. By examining the effect of a realistic diffusion mechanism in systems undergoing phase transformation, a critical discussion of time scales in microscopic mean field models and a Monte Carlo model with Kawasaki dynamics is presented.

Através do uso de reagentes ambientalmente corretos, foram desenvolvidos métodos mais simples que os tradicionais para obtenção de diversos tipos de nanopartículas de magnetita (MagNP) funcionalizadas. Em todos os casos foi confirmado um comportamento superparamagnético consistente com a presença de monodomínios magnéticos de Fe3O4, com diâmetros médios de partícula inferiores a 100 nm, além de histerese nula acima de 280 K, Tb=90K em H=500 Oe e magnetização de saturação em torno de 90 emu g-1. Os métodos de síntese das MagNP foram conduzidos em solventes derivados do biodiesel de soja/mamona, em substituição ao insumos importados, permitindo uma redução significativa nos custos de produção desse tipo de nanomaterial, e viabilizando sua produção em larga escala. Os nanomateriais foram voltados inicialmente para captura, separação e reciclagem de insumos e produtos químicos, incluindo poluentes, catalisadores e enzimas, utilizando ímãs externos. Os procedimentos desenvolvidos proporcionaram uma alternativa verde para os processos convencionais que fazem uso extensivo de solventes, geram muito descarte, e utilizam processos com alta demanda de energia, como centrifugação, extração por solventes e filtração sob altas pressões. As MagNP foram especialmente projetadas para serem dispersas em diversos meios polares e apolares, de acordo com o tipo de funcionalização química na superfície, utilizando principalmente moléculas orgânicas anfifílicas capazes de se ligar na superfície do Fe3O4 por meio de grupos polares, e com matrizes carbonáceas por meio de interações hidrofóbicas. Dessa forma foram gerados novos nanomateriais superparamagnéticos incorporando diversos tipos de matrizes que foram testadas para a remoção de óleo e de compostos orgânicos responsáveis por odores e cores indesejadas em efluentes industriais, bem como para a captura, transporte, recuperação, análise de espécies metálicas ou orgânicas. Foram testadas janelas ópticas e displays nos quais a intensidade de luz transmitida ou refletida pode ser modulada com ímãs externos. O projeto, financiado pela PETROBRÁS contemplou ainda outras aplicações sigilosas, que foram omitidas desta tese. Seu andamento abriu uma importante janela em prol da sustentabilidade, levando ao início do desenvolvimento no Laboratório, da nanomagneto-hidrometalurgia verde para obtenção e reciclagem de metais estratégicos, e de trabalhos de despoluição magnética de ambientes contaminados. / New routes for low cost production of functionalized magnetic nanoparticles (MagNP) have been pursued in this Thesis, by employing environmentally compatible chemicals and resources. The nanomaterials exhibited typical superparamagnetic behavior consistent with the presence of magnetic monodomains, revealing no hysteresis above 280 K, Tb = 90 K at H = 500 Oe, and saturation magnetization as high as 90 emu g-1. The synthetic procedures were carried out using biocompatible solvents derived from biodiesel of soybean and Brazilian mamona seeds, leading to substantial reduction of cost for large-scale production. The superparamagnetic nanoparticles were initially designed for capturing, transporting and recycling chemicals or drugs, including pollutants, catalysts and enzymes, using external magnets. They provide a green alternative strategy for conventional processes that make extensive use of solvents, generate too much waste, and proceeds through highly energetic demanding steps such as centrifugation, solvent extraction and high-pressure filtration. In our work, the MagNPs were appropriately modified for working in polar and non-polar media, employing for instance, amphiphilic species for interacting with Fe3O4 using the available polar groups, and also with carbon surfaces by means of hydrophobic interactions. Accordingly, new superparamagnetic nanomaterials incorporating several types of materials carbon based. It was observed that the carbon materials containing 15 to 20% of magnetic nanoparticles could be completely removed from the media with the use of a magnet. In this way, the functionalized superparamagnetic nanoparticles proved useful for the removal of oil spills and of organic pollutants from industrial processing water, as well as for the capture, removal and recovery of metallic elements and organic species from the effluents. In addition, as a proof of concept, smart windows and displays were elaborated based on the modulation of the transmitted or reflected light by the external magnet. This work was sponsored by PETROBRÁS, and also covered missing, non-authorized aspects involved in two patent applications. Finally, an important consequence to be mentioned is the contribution of this project for launching new chemical routes towards sustainability, such as the development in this Laboratory, of green, magnetic nano-hydrometalurgy for processing and recycling strategic metals, and of the magnetic remediation of polluted environments using the functionalized nanomaterials.

This is the first study comparing morphologies of CNT films on Kanthal wire, with their field emission properties, and as such offers ways to design better cylindrical emitter devices. A low turn-on field was achieved (0.35 V/µm), the field emission results have been explained using a simple model, and a fluorescent lamp was fabricated. Whilst previous work has been done on the link between “as grown” CNT films and their respective field emission properties on flat substrates, very little work has been done on linking morphology to emission performance on wire substrates, where the morphology can be very different. Microscopic structures such as towers, ridges and clumps consisting of many aligned or entangled CNTs were grown using an aerosol chemical vapour deposition (a-CVD) technique. Hydrogen added to the carrier gas resulted in a decrease in defect density in the growth of undoped CNTs, and an increase in defect density in the growth of nitrogen doped CNTs (N-CNTs) and boron doped CNTs (BCNTs). In-situ transmission electron microscopy (TEM) studies show that damage to CNT tips results in a significantly higher turn-on field compared to undamaged tips. This can be recovered by making the CNT emit current for several minutes which makes the tip recrystallize due to heat caused by the Nottingham effect. The field emission properties of the “as grown” CNT films are dominated by protruding CNTs found at the edges of ridge and tower microscopic structures. The field emission properties are also related to the dimensions of these structures with the longest ridges (hence those with the longest protruding CNTs) resulting in the lowest turn-on electric field. The ridge and tower structures act to accommodate protruding CNTs at their edges and their physical dimensions (mainly width) act to separate these emitters so that screening is minimised. This work shows that efficient emitters can be fabricated effectively from simple a-CVD techniques and microscopic structures act to improve, not degrade, field emission properties.

Artificial tissue expansion is required to generate new skin prior to reconstructive surgery, in order to compensate for a deficit of healthy tissue. Hydrogel tissue expanders, which expand anisotropically, show great promise in overcoming clinical limitations in the field, thus allowing the technique to be used in a wider range of surgeries. These devices consist of pellets of dry poly(methyl methacrylate-co-vinylpyrrolidone), compressed into discs through a hot compression moulding process. However, a number of significant problems still exist in these devices, and this thesis aims to address these issues. To date, there has been a lack of investigation of the factors governing the behaviour of anisotropic swelling. For this reason, a range of different compression ratios have been investigated, with particular focus on the relationship between the material flow during compression and the swelling behaviour of the resulting device. It was found that samples of the same initial size expand to the same reference swelling dimensions, regardless of compression ratio. During hot pressing, the material flow was found to be governed by slip-stick behaviour at the interface between the hot press and the device, affecting the properties and swelling behaviour of the devices. Based on these findings, devices were developed which could expand from a disc into a non-prismatic shape (dome or wedge). Such devices could reduce complication rates and allow the growth of new tissue with anisotropic resting tension. The devices were tested in a small in vivo trial, where it was shown that there were no adverse effects on the tissue produced, and that the shape of the expander (dome) was retained. As devices are being produced for medical use, understanding the effect of sterilization by &gamma;-irradiation is essential, but to date this has been overlooked in the literature. It was found that γ-irradiation caused an increase in cross-linking in the P(MMA-co-NVP). Whilst this produced little change in swelling behaviour for isotropic devices, in the case of anisotropic devices it caused a change in the shape of expansion, reducing the area of new skin which could be generated by the device. It was found that by reducing the concentration of impurities (residual molecules from the polymer synthesis) the impact of &gamma;-irradiation could be greatly reduced. Finally, controlling the rate of expansion is essential in order to avoid clinical complications. In order to control the rate of expansion, particularly during the initial period of swelling, semi-permeable PDMS coatings were applied to the compressed devices. Coatings of thickness greater than 0.375mm were found to effectively control the rate of swelling, for both cylindrical and non-prismatic shapes. As the coating thickness increased, the maximum swelling size decreased. However, it has been shown that change in height (the parameter which governs the area of skin produced) is affected less than the change in mass or diameter.

Organic and hybrid organic-inorganic photovoltaic (PV) devices have the potential to provide low-cost, large scale renewable energy. Despite the tremendous progress that has been made in this field, device efficiencies remain low. This low efficiency can be partly attributed to the low open-circuit voltages (Voc) generated by organic and hybrid organic-inorganic PV devices. The Voc is critically determined by the energy-level alignment at the interface between the materials forming the device. In this thesis we use first-principles methods to explore the energy-level alignment at the interfaces between the conjugated polymer poly(3-hexylthiophene) (P3HT) and three electron acceptors, zinc oxide (ZnO), gallium arsenide (GaAs) and graphene. We find that Voc reported in the literature for ZnO/P3HT devices is significantly lower than the theoretical maximum and that the interfacial electrostatic dipole plays an important role in the physics underlying the charge transfer at the heterojunction. We note significant charge transfer from the polymer to the semiconductor at GaAs/P3HT interfaces, and use this result to help interpret experimental data. Our findings support the conclusion that charge transferred from P3HT to GaAs nanowires can passivate the surface defect states of the latter and, as a result, account for the observed decrease in photoluminescence lifetimes. Finally, we explore the energy-level alignment at the graphene/P3HT interface and find that Voc reported for experimental devices is in line with the theoretical maximum. The effect of functionalised graphene is also examined, leading to the suggestion that functionalisation might have important consequences for device optimisation.