Organic solar cells have unique properties that make them very attractive as a renewable energy source. Of particular interest are semi-transparent cells, which have the potential to be integrated into building façades yet not completely block light. However, making organic cells transparent limits the metal electrode thickness to a few nanometres, drastically reducing its reflectivity and the device photon-harvesting capacity. Here, we propose and implement an ad hoc path for light-harvesting recovery to bring the photon-to-charge conversion up to almost 80% that of its opaque counterpart. We report semi-transparent PTB7:PC 71 BM cells that exhibit 30% visible light transmission and 5.6% power conversion efficiency. Non-periodic photonic crystals are used to trap near-infrared and near-ultraviolet photons. By modifying the layer structure it is possible to tune the device colour without significantly altering cell performance.

Nanoporous ZnO thin films presenting a tunable nanostructure and photoluminescence (PL) were grown by plasma enhanced vapor deposition on surface oxidized Si substrates. These films consist of c-axis oriented wurtzite ZnO nanocolumns whose topology, crystallinity, and PL can be tuned through the substrate temperature (varied in the 300-573 K range) and the nature of the plasma assistance (pure O 2 , O 2 /Ar, O 2 /H 2 , or O 2 /N 2 mixture). In particular, these processing parameters influence the intensity of the UV and visible PL bands of the films, related to excitonic and defective radiative transitions, respectively. Increasing the substrate temperature enhances the UV PL and rubs out the visible PL due to the increase of grain size and the removal of interstitial defects. Additional tuning of the intensity ratio between the UV and visible bands can be done by controlling the film thickness. A decrease of the UV PL is observed when the films go thicker, an effect that is likely to be linked to the microstructure of the films rather than to their crystallinity that is improved upon increasing of the film thickness, as seen from PL spectroscopy and XRD measurements. Indeed, a gradient of stress, decreasing from the substrate to the surface, is evidenced and related to a concentration gradient of interstitial defects. The drawbacks of the thickness effect, which prohibits growing thick films with a high optical quality, can be bypassed by growing the films in a O 2 /H 2 plasma.

Plasmonic photodetectors are attracting the attention of the photonics community. Plasmonics is attractive because metallic structures have the ability to confine light by coupling an electromagnetic wave to charged carrier oscillations at the surface of the metal. The wavelength of such oscillations can be much smaller than the corresponding light wavelength in vacuum. This enables the light-matter interaction on a deep subwavelength scale, which in turn allows for more compact and potentially higher speed devices. In this review, we discuss different types of photodetectors and ways in which plasmonics can be applied to them. We elucidate several plasmonic photodetector concepts/schemes and discuss the main physical principles behind their operation. Finally, we reflect on the characteristics of an "ideal" photodetector and propose a device that might be the perfect plasmonic detector.

In this article we present a new type of 1D nanostructures consisting of supported hollow ZnO nanorods (NRs) decorated with Ag nanoparticles (NPs). The 3D reconstruction by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) electron tomography reveals that the Ag NPs are distributed along the hollow interior of the ZnO NRs. Supported and vertically aligned Ag-NPs@ZnO-NRs grow at low temperature (135 C) by plasma enhanced chemical vapour deposition on heterostructured substrates fabricated by sputtered deposition of silver on flat surfaces of Si wafers, quartz slides or ITO. The growth mechanisms of these structures and their wetting behavior before and after visible light irradiation are critically discussed. The as prepared surfaces are superhydrophobic with water contact angles higher than 150. These surfaces turn into superhydrophilic with water contact angles lower than 10 after prolonged irradiation under both visible and UV light. The evolution rate of the wetting angle and its dependence on the light characteristics are related to the nanostructure and the presence of silver embedded within the ZnO NRs.

We show that the tilt angle of nanostructures obtained by glancing angle sputtering is finely tuned by selecting the adequate argon pressure. At low pressures, a ballistic deposition regime dominates, yielding high directional atoms that form tilted nanocolumns. High pressures lead to a diffusive regime which gives rise to vertical columnar growth. Monte Carlo simulations reproduce the experimental results indicating that the loss of directionality of the sputtered particles in the gas phase, together with the self-shadowing mechanism at the surface, are the main processes responsible for the development of the columns.

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Abstract. The microstructural features of amorphous TiO2 thin films grown by the electron beam physical vapour deposition technique at oblique angles have been experimentally and theoretically studied. The microstructural features of the deposited films were characterized by considering both, the column tilt angle and the increase of the column thickness with height. A Monte Carlo model of the film growth has been developed that takes into account surface shadowing, short-range interaction between the deposition species and the film surface, as well as the angular broadening of the deposition flux when arriving at the substrate. The good match between simulations and experimental results indicates the importance of these factors in the growth and microstructural development of thin films deposited at oblique angles.

Transparent nanocolumnar porous ZnO thin films have been prepared by plasma-enhanced chemical vapor deposition. By controlling the H2/O2 ratio in the plasma gas, the deposition conditions were optimized to obtain an intense exciton emission at around 381 nm and virtually no luminescence in the visible region associated with electronic states in the gap. The intensity of the exciton band varied significantly and reversibly with the partial pressure of oxygen in the environment. This behavior and its variations with temperature and water vapor sustain the use of these thin films as photonic sensors of oxygen. Further experiments in liquid water show that fluorescence intensity also varies with the amount of dissolved oxygen even for concentrations lower than 0.02 mg/L where commercial oxygen galvanic sensors show limited sensitivity. These results and the use of ZnO as photonic sensor of oxygen are discussed by assuming a classical mechanism involving the photoactivated adsorption of oxygen when this oxide is irradiated with UV light during its fluorescence interrogation.