General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms AbstractIn a quest to fabricate novel solar energy materials, the high quantum efficiency and long charge separated states of photosynthetic pigment-proteins are being exploited through their direct incorporation in bioelectronic devices. In this work, photocurrent generation by bacterial reaction center-light harvesting 1 (RC-LH1) complexes self-assembled on a nanostructured silver substrate yielded a peak photocurrent of 166 µA cm -2 under 1 sun illumination, and a maximum of over 400 µA cm -2 under 4 suns, the highest reported to date.A 2.5-fold plasmonic enhancement of light absorption per RC-LH1 complex was measured on the rough silver substrate. This plasmonic interaction was assessed using confocal fluorescence microscopy, revealing an increase of fluorescence yield and radiative rate of the RC-LH1 complexes. Nano-structuring of the silver substrate also enhanced the stability of the protein under continuous illumination by almost an order of magnitude relative to a nonstructured bulk silver control. Due to its ease of construction, increased protein loading capacity, stability and more efficient use of light, this hybrid material is an excellent candidate for further development of plasmon enhanced biosensors and bio-photovoltaic devices.3

Insights to the mechanism of CdSe nanoparticle attachment to carbon nanotubes following the hot injection method are discussed. It was observed that the presence of water improves the nanotube coverage while Cl containing media are responsible for the shape transformation of the nanoparticles and further attachment to the carbon lattice. The experiments also show that the mechanism taking place involves the right balance of several factors, namely, low passivated nanoparticle surface, particles with well-defined crystallographic facets, and interaction with an organics-free sp 2 carbon lattice. Furthermore, this procedure can be extended to cover graphene by quantum dots.The extraordinary properties of nanosized materials have boosted intensive work in the development of several synthetic methodologies in the last decades. The so called hot injection method [1] is, among them, a versatile and relatively cheap means that nowadays provides a high degree of perfection, reproducibility and control of semiconductor [2,3], and magnetic [1, 4] nanocrystals. This colloidal synthetic route is based on the reaction of highly reactive species in media where surfactants play an essential role in the final shape, size, and stability of the desired nanomaterial. However, small variations in monomer concentrations, temperatures, time, or presence of impurities may drive the reaction into different regimes. As a consequence, diverse sizes, shapes, and compositions of nanoparticles can be obtained. A. J. Houtepen et al. [5] describes the role of acetate in the synthesis of PbSe nanoparticles. Traces of acetate can be responsible for a great variety of nanoparticles shapes. It is also known that small traces of phosphonic acids can influence decisively the mechanism, the yield, and the shape of the nanoparticles [6,7,8]. Recently, the hot injection method was also followed to produce composites of CdSe semiconductor nanoparticles and carbon nanotubes (CdSe-CNTs) [9,10,11]. It was observed that in the presence of CNTs, CdSe nanorods evolved into pyramidal-like nanoparticles that connected to CNTs by the wurtzite (001) facets [9,10,11,12]. Furthermore, rods and pyramidal-like nanoparticles showed different interaction with CNTs, the latter showing a clear tendency to attach to the carbon lattice. Unlike heterogeneous growth on a seed surface, the reaction of CdSe nanorods in the presence of carbon nanotubes proceeds independently of the carbon lattice during their nucleation and growth. The proposed mechanism so far [9] suggested that the shape transformation of the nanoparticles as a result of nanotube-nanoparticle interaction and a decisive role of octadecylphosphonic acid (ODPA). ODPA is used as complexing agent of the cadmium source and acts as capping ligand of the nanoparticles at Cd sites [13].In this letter, we address the influence of the CNTs dis- * Electronic address: hernande@chemie.uni-hamburg.de persant (solvent) and water on the shape of the nanoparticles and the requirements for further attachment to the carbon latt...

We describe the synthesis and spectroscopic characterization of colloidal ZnSe/ZnS/CdS nanocrystals, which exhibit a type-II electronic structure and wave function overlap that is strongly dependent on the thickness of the ZnS barrier. Barrier thickness is controlled by both the amount of deposited material and the reaction and annealing temperature of CdS shell growth. The results show that a single monolayer of ZnS mitigates the overlap significantly, while four and more monolayers effectively suppress band edge absorption and emission. Transient absorption spectra reveal a broad distribution of excitons with mixed S and P symmetry, which become allowed due to alloy formation and contribute to charge carrier relaxation across the barrier. We present a model of the core/shell interface based on cation diffusion, which allows one to estimate the extent of the diffusion layer from optical spectra.

ZnO is a promising catalyst for hydrogen and oxygen production due to the position of the conduction and valence bands. Nevertheless, there are some limitations to the efficiency due to its n-type character. Once in contact with the electrolyte, an extraction barrier for electrons is formed. The purpose of this work was to create an extraction site for electrons by synthesizing small pyramidally shaped ZnO nanocrystals (∼10 nm), which consist of a predefined site for the growth of a gold particle at the tip. Photoelectrochemical deposition of gold on ZnO was performed to yield the hybrid structure. Photoluminescence (PL) studies of the relative change of intensities of band gap versus defect state relaxation showed electron transfer from the conduction band of ZnO to Au. Using cyclic voltammetry, Aumediated charge extraction from Au−ZnO hybrids was demonstrated, which circumvents the electron extraction barrier in ZnO. Thus, this work demonstrates the nanoscale design of hybrid structures for photocatalytic applications.

[ 6 ] and phenyl-C71-butyric acid methyl ester (PC 70 BM). [ 2 , 7 ] Despite promising results, the performance of PTB7:PC 70 BM solar cells is limited by the thin active layer, [ 3 ] carrier selectivity at the contacts, [ 8 ] and rapid degradation of the active layer and contacts caused by exposure to ambient oxygen [9][10][11] and water vapor. [ 12 ] Although inverted solar cell architectures have demonstrated high effi ciencies combined with relatively good stability, age-induced performance loss in high performance PTB7 solar cell architectures [ 2 ] has been reported, and the mechanisms are currently not well understood.Identifying the origins of performance loss in solar cells is challenging because it involves differentiating between interfacial phenomena and bulk properties. [ 13 ] Frequency resolved optoelectronic techniques such as impedance spectroscopy [ 14 ] and intensity modulated photocurrent spectroscopy (IMPS) [ 15 ] are useful in discriminating between electronic processes in the active layer and at contact interfaces, and correlating these with device performance. In this work, we combine these techniques with device modeling to identify key loss processes and aging mechanisms in state-of-the-art PTB7-based inverted solar cells incorporating a V 2 O 5 hole transport layer. After prolonged exposure to ambient conditions no change in the open circuit voltage ( V oc ) or short circuit current density ( J sc ) was observed. An s-shape is initially observed in the current density -voltage ( J -V) characteristic, which can be reversed by cycling through the J -V curve under illumination. Subsequently, a small drop in the fi ll factor (FF) from the original value of 0.7 to 0.61 was observed. With impedance spectroscopy, we demonstrate that changes to the device interfaces are completely reversible, and that performance losses related to the FF are due to degradation of the organic active layer. The IMPS analysis reveals age-related trap formation in the active layer. Interestingly, the high density of traps does not appear to have a signifi cant effect on performance. We attribute this phenomenon to slow carrier thermalization times. ResultsThe device structure is depicted in Figure 1 a. The PTB7:PC 70 BM active layer was sandwiched between an Indium tin oxide (ITO)/ poly [(9,9-bis(3-( N , N -dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfl uorene)] (PFN) [ 16 ] electron extracting contact