Artículos SCI

The eventual exploitation of one-dimensional nanomaterials needs the development of scalable, high yield, homogeneous and environmentally friendly methods capable of meeting the requirements for fabrication of functional nanomaterials with properties on demand. In this article, we demonstrate a vacuum and plasma one-reactor approach for the synthesis of fundamental common elements in solar energy and optoelectronics, i.e. the transparent conducting electrode but in the form of nanotube and nanotree architectures. Although the process is generic and can be used for a variety of TCOs and wide-bandgap semiconductors, we focus herein on indium doped tin oxide (ITO) as the most previously researched in previous applications. This protocol combines widely applied deposition techniques such as thermal evaporation for the formation of organic nanowires serving as 1D and 3D soft templates, deposition of polycrystalline layers by magnetron sputtering, and removal of the templates by simply annealing under mild vacuum conditions. The process variables are tuned to control the stoichiometry, morphology, and alignment of the ITO nanotubes and nanotrees. Four-probe characterization reveals the improved lateral connectivity of the ITO nanotrees and applied on individual nanotubes shows resistivities as low as 3.5 +/- 0.9 x 10(-4) omega cm, a value comparable to that of single-crystalline counterparts. The assessment of diffuse reflectance and transmittance in the UV-Vis range confirms the viability of the supported ITO nanotubes as random optical media working as strong scattering layers. Their further ability to form ITO nanotrees opens a path for practical applications as ultra-broadband absorbers in the NIR. The demonstrated low resistivity and optical properties of these ITO nanostructures open a way for their use in LEDs, IR shields, energy harvesting, nanosensors, and photoelectrochemical applications.

Herein, both from the experimental and theoretical point of view, the optical absorption properties of a subphthalocyanine (SubPc), an organic macrocycle commonly used as a sunlight harvester, coupled to metallic optical cavities are analyzed. How different electronic transitions characteristic of this compound and specifically those that give rise to excitonic (Q band) and charge transfer (CT band) transitions couple to optical cavity modes is investigated. It is observed that whereas the CT band couples weakly to the cavity, the Q band transitions show evidence of hybridization with the photon eigenstates of the resonator, a distinctive trait of the strong coupling regime. As a result of the different coupling regimes of the two electronic transitions, very different spectral and directional light-harvesting features are observed, which for the weakly coupled CT transitions are mainly determined by the highly dispersive cavity modes and for the strongly coupled Q band by the less angle-dependent exciton-polariton bands. Modeling also allows discriminating parasitic from productive absorption in each case, enabling the estimation of the expected losses in a solar cell acting as an optical resonator.