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In this paper, we present a study of silicon surface passivation based on the use of spin-coated hybrid composite layers. We investigate both undoped poly(3,4-ethylenedioxythiophene)/poly-(styrenesulfonate) (PEDOT:PSS), as well as PEDOT:PSS functionalized with semiconducting oxide nanomaterials (TiO and SnO). The hybrid compound was deposited at room temperature by spin coating-a potentially lower cost, lower processing time and higher throughput alternative compared with the commonly used vacuum-based techniques. Photoluminescence imaging was used to characterize the electronic properties of the Si/PEDOT:PSS interface. Good surface passivation was achieved by PEDOT:PSS functionalized by semiconducting oxides. We show that control of the concentration of semiconducting oxide nanoparticles in the polymer is crucial in determining the passivation performance. A charge carrier lifetime of about 275 μs has been achieved when using SnO nanoparticles at a concentration of 0.5 wt.% as a filler in the composite film. X-ray diffraction (XRD), scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), energy dispersive x-ray in an SEM, and μ-Raman spectroscopy have been used for the morphological, chemical and structural characterization. Finally, a simple model of a photovoltaic device based on PEDOT:PSS functionalized with semiconducting oxide nanoparticles has been fabricated and electrically characterized.

Nickel oxide (NiO) is one of the very few p-type semiconducting oxides, the study of which is gaining increasing attention in recent years due to its potential applicability in many emerging fields of technological research. Actually, a growing number of scientific works focus on NiO-based electrochromic devices, high-frequency spintronics, fuel cell electrodes, supercapacitors, photocatalyst, chemical/gas sensors, or magnetic devices, among others. However, less has been done so far in the development of NiO-based optical devices, a field in which this versatile transition metal oxide still lags in performance despite its potential applicability. This review could contribute with novelty and new forefront insights on NiO micro and nanostructures with promising applicability in optical and optoelectronic devices. As some examples, NiO lighting devices, optical microresonators, waveguides, optical limiters, and neuromorphic applications are reviewed and analyzed in this work. These emerging functionalities, together with some other recent developments based on NiO micro and nanostructures, can open a new field of research based on this p-type material which still remains scarcely explored from an optical perspective, and would pave the way to future research and scientific advances.

The potential use of NiO in low-dimensional devices requires the upgrade of appropriate synthesis methods as well as the achievement of a deeper comprehension of the growth mechanisms and the properties of this p-type oxide at the micro- and nanoscale. In this work, arrays of NiO microcavities with potential use in catalysis, sensing, and high temperature templates have been achieved following a single step process based on the use a controlled argon flow during oxidation of metallic Ni. Fabrication of these self-organized cavities can widen the applicability of NiO in new fields of research avoiding large cost post-fabrication treatments and enhancing NiO properties of interest. Formation of these hole arrays at 1000–1200 °C with unique geometrical morphology and preferential (111) texturing has been discussed based on Ni oxidation mechanisms involving Ni lattice diffusion and strain release phenomena at the NiO surface. Moreover, NiO samples have been fabricated in the range of temperatures 800–1500 °C and characterized by a complete group of techniques in order to shed light on physical aspects related to NiO which still remain unambiguous, such as the bandgap or the understanding of the Raman signal. XRD measurements confirm the presence of strain related phenomena and lattice distortions during thermal treatments. Besides, cathodoluminescence analysis shows a wide signal from near-IR to UV commonly dominated by an emission at 2.5 eV related to Ni deficiency. An increase in the Ni3+/Ni2+ ratio together with a higher p-type character, as demonstrated by surface-sensitive X-ray photoelectron spectroscopy, was promoted in the regions with microcavities as well as in the samples sintered at high temperature.

Transition metal oxides potentially present higher specific capacities than the current anodes based on carbon, providing an increasing energy density as compared to commercial Li-ion batteries. However, many parameters could influence the performance of the batteries, which depend on the processing of the electrode materials leading to different surface properties, sizes or crystalline phases. In this work a comparative study of tin and titanium oxide nanoparticles synthesized by different methods, undoped or Li doped, used as single components or in mixed ratio, or alternatively forming a composite with graphene oxide have been tested demonstrating an enhancement in capacity with Li doping and better cyclability for mixed phases and composite anodes.