In this study, we report solution-processed amorphous zinc tin oxide transistors exhibiting high operational stability under positive gate bias stress, translated by a recoverable threshold voltage shift of about 20{%} of total applied stress voltage. Under vacuum condition, the threshold voltage shift saturates showing that the gate-bias stress is limited by trap exhaustion or balance between trap filling and emptying mechanism. In ambient atmosphere, the threshold voltage shift no longer saturates, stability is degraded and the recovering process is impeded. We suggest that the trapping time during the stress and detrapping time in recovering are affected by oxygen adsorption/desorption processes. The time constants extracted from stretched exponential fitting curves are ≈106 s and 105 s in vacuum and air, respectively.

Aluminium-doped zinc oxide (AZO) is a common material used as a front contact layer on chalcopyrite CuInGaSe2 (CIGS)-based thin-film solar cells since it combines optimum optical and electrical properties with low cost and abundant elemental availability. Low-resistivity and high-transmission front contacts are required to develop high-performance CIGS solar cells. However, the durability of the cells is highly influenced by the corrosion resistance behaviour of the AZO layers. In this work, an exhaustive study of the aluminium-doped zinc oxide layers (AZO) deposited by pulsed DC magnetron sputtering (MS) has been performed. The optical, electrical and electrochemical corrosion resistance properties of the AZO layers have been evaluated as a function of the deposition pressure. The results show that adjusting the deposition pressure could develop AZO layers with very high electrochemical corrosion resistance in chlorinated aqueous media combined with optimum electrical and optical properties. Layers grown at 3×10−3mbar pressure present very high corrosion resistance values (in the order of 106 {\$}Ømega{\$}) and very high electrochemical stability, indicating no tendency for electrochemical corrosion degradation. Besides, these layers are highly transparent with an average transmittance in the visible range above 90{%} and with a low resistivity of 6.8×10−4 {\$}Ømega{\$}cm for a 1000nm films thickness, making them optimum candidate front contact for high-performance and high durability CIGS solar cells.

Electrochemically active bacteria (EAB) have the capability to transfer electrons to cell exterior, a feature that is currently explored for important applications in bioremediation and biotechnology fields. However, the number of isolated and characterized EAB species is still very limited regarding their abundance in nature. Colorimetric detection has emerged recently as an attractive mean for fast identification and characterization of analytes based on the use of electrochromic materials. In this work, WO3 nanoparticles were synthesized by microwave assisted hydrothermal synthesis and used to impregnate non-treated regular office paper substrates. This allowed the production of a paper-based colorimetric sensor able to detect EAB in a simple, rapid, reliable, inexpensive and eco-friendly method. The developed platform was then tested with Geobacter sulfurreducens, as a proof of concept. G. sulfurreducens cells were detected at latent phase with an RGB ratio of 1.10 ± 0.04, and a response time of two hours.

Here we present for the first time a TiO2/Cu2O all-oxide heterojunction solar cell entirely produced by spray pyrolysis onto fluorine doped tin oxide (FTO) covered glass substrates, using silver as a back contact. A combinatorial approach was chosen to investigate the impact of the TiO2 window layer and the Cu2O light absorber thicknesses. We observe an open circuit voltage up to 350mV and a short circuit current density which is strongly dependent of the Cu2O thickness, reaching a maximum of {\~{}}0.4mA/cm2. Optical investigation reveals that a thickness of 300nm spray pyrolysis deposited Cu2O is sufficient to absorb most photons with an energy above the symmetry allowed optical transition of 2.5eV, indicating that the low current densities are caused by strong recombination in the absorber that consists of small Cu2O grains.

In this work we report the role of thickness on electrochromic behavior of nickel oxide (NiO) films deposited by e-beam evaporation at room temperature on ITO-coated glass. The structure and morphology of films with thicknesses between 100 and 500 nm were analyzed and then correlated with electrochemical response and transmittance modulation when immersed in 0.5 M LiClO4–PC electrolyte. The NiO exhibits an anodic coloration, reaching for the thickest film a transmittance modulation of 66{%} between colored and bleached state, at 630 nm, with a color efficiency of 55 cm2 C−1. Very fast switch between states was obtained, where coloration and bleaching times are 3.6 s cm−2 and 1.4 s cm−2, respectively.

Cotton-based nanocrystalline cellulose (NCC), also known as nanopaper, one of the major sources of renewable materials, is a promising substrate and component for producing low cost fully recyclable flexible paper electronic devices and systems due to its properties (lightweight, stiffness, non-toxicity, transparency, low thermal expansion, gas impermeability and improved mechanical properties). Here, we have demonstrated for the first time a thin transparent nanopaper-based field effect transistor (FET) where NCC is simultaneously used as the substrate and as the gate dielectric layer in an ‘interstrate' structure, since the device is built on both sides of the NCC films; while the active channel layer is based on oxide amorphous semiconductors, the gate electrode is based on a transparent conductive oxide. Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility ({\textgreater}7 cm 2 V −1 s −1 ), drain–source current on/off modulation ratio higher than 10 5 , enhancement n-type operation and subthreshold gate voltage swing of 2.11 V/decade. The NCC film FET characteristics have been measured in air ambient conditions and present good stability, after two weeks of being processed, without any type of encapsulation or passivation layer. The results obtained are comparable to ones produced for conventional cellulose paper, marking this out as a promising approach for attaining high-performance disposable electronics such as paper displays, smart labels, smart packaging, RFID (radio-frequency identification) and point-of-care systems for self-analysis in bioscience applications, among others.

Paper electronics is a topic of great interest due the possibility of having low-cost, disposable and recyclable electronic devices. The final goal is to make paper itself an active part of such devices. In this work we present new approaches in the selection of tailored paper, aiming to use it simultaneously as substrate and dielectric in oxide based paper field effect transistors (FETs). From the work performed, it was observed that the gate leakage current in paper FETs can be reduced using a dense microfiber/nanofiber cellulose paper as the dielectric. Also, the stability of these devices against changes in relative humidity is improved. On other hand, if the pH of the microfiber/nanofiber cellulose pulp is modified by the addition of HCl, the saturation mobility of the devices increases up to 16 cm 2 V −1 s −1 , with an I ON / I OFF ratio close to 10 5 .

The present work focuses on a qualitative analysis of localised I-V characteristics based on the nanostructure morphology of highly dense arrays of p-type NiO nano-pillars (NiO-NPs). Vertically aligned NiO-NPs have been grown on different substrates by using a glancing angle deposition (GLAD) technique. The preferred orientation of as grown NiO-NPs was controlled by the deposition pressure. The NiO-NPs displayed a polar surface with a microscopic dipole moment along the (111) plane (Tasker's type III). Consequently, the crystal plane dependent surface electron accumulation layer and the lattice disorder at the grain boundary interface showed a non-uniform current distribution throughout the sample surface, demonstrated by a conducting AFM technique (c-AFM). The variation in I-V for different points in a single current distribution grain (CD-grain) has been attributed to the variation of Schottky barrier height (SBH) at the metal-semiconductor (M-S) interface. Furthermore, we observed that the strain produced during the NiO-NPs growth can modulate the SBH. Inbound strain acts as an external field to influence the local electric field at the M-S interface causing a variation in SBH with the NPs orientation. This paper shows that vertical arrays of NiO-NPs are potential candidates for nanoscale devices because they have a great impact on the local current transport mechanism due to its nanostructure morphology.