In organic photovoltaic devices, outer interface structures play a significant role in establishing optimal contact conditions for efficient extraction (or blocking) of charge carriers. Buffer layers of different nature are currently employed to enhance both power conversion efficiency (PCE) and cell stability by improving contact performance. Several materials have been explored to enhance the electron selectivity of the cathode contact: alkali metal compounds (LiF, etc.), metal oxides (TiO x , ZnO, etc.), and low molecular weight organic compounds have been reported to contribute to the overall PCE and solar cell lifetime, as reviewed in recent reports.1À3 Among those approaches, the effect of the dipole moment associated with self-assembled monolayers (SAM) attached to the interface, which alter the energy level alignment between the cathode metal and the bulk of the blend, 4 is particularly interesting, as well as the inclusion of conjugated polyelectrolyte interlayers. 5 In all of these cases, the energy shift induced by the charge dipole built up at interface layers enables the use of air-stable high work function metals. It is then inferred that electrostatic mechanisms occurring at the nanometer scale, both in the active layer bulk and at interfaces, have a great influence on the overall device operation. 6,7 Interface dipole layers are regarded as a determining ingredient of the metal/organic contact equilibration. 8À12 Several models have been proposed to account for the energy level alignment at interfaces, depending on the degree of interaction between the metal contact and the deposited organic layer. When the chemical interaction between the metal and contacting conjugated molecules or polymers is not negligible, it is expected that molecules attached to the metal surface undergo both a shift and a broadening of their molecular energy levels. Energy distribution of the attached molecules should be modeled by a specific interfacial density of states (IDOS) which differs from that encountered in the bulk of the organic layer. The situation is

A connection is established between recombination and series resistances extracted from impedance spectroscopy and current‐voltage curves of polythiophene:fullerene organic solar cells. Recombination is shown to depend exclusively on the (Fermi level) voltage, which allows construction of the current‐voltage characteristics in any required conditions based on a restricted set of measurements. The analysis highlights carrier recombination current as the determining mechanism of organic solar cell performance.

In this paper, the electrochemical degradation of polypyrrole film was studied by means of overpotential application. The overpotential was 0.58 V versus SCE, and after every 5 min of application of 0.58 V, a cyclic voltammogram was recorded in the range of -0.7 to 0.5 V as well as an electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance (EIS and EQCM). The main characteristic is the huge increase in the charge transfer resistance (r(ct)), which indicates that the insertion process of ions in the polymer matrix is hindered by the electrochemical degradation. Once the process of insertion is damaged, the number of intercalated ions in the matrix should decrease, which is expressed by the low-frequency capacitance, which is proportional to the number of intercalated ions in the polymeric matrix. The decrease of intercalated ions has an influence in the mass variation of the polymer film, which is confirmed by EQCM measurements.

This work investigates the loss in performance induced by molecular oxygen in bulk heterojunction solar cells. We observe that upon exposure to molecular oxygen both formation of P3HT

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The rapid and reliable detection of SARS-CoV-2 seroconversion in humans is crucial for suitable infection control. In this sense, many studies have focused on increasing the sensibility, lowering the detection limits and minimizing false negative/positive results. Thus, biosensors based on nanoarchitectures of conducting polymers (CPs) are promising alternatives to more traditional materials, since they can hold improved surface area, higher electrical conductivity and electrochemical activity. In this work, we reported the analytical comparison of two different CPs morphologies for the development of an impedimetric biosensor to monitor SARS-CoV-2 seroconversion in humans. Biosensors based on polypyrrole (PPy), synthesized in both globular and nanotubular (NTs) morphology, and gold nanoparticles (AuNPs) are reported, using a self-assembly monolayer of 3-mercaptopropionic acid and covalently linked SARS-CoV-2 Nucleocapsid protein. Firstly, the novel hybrid materials were characterized by electron microscopy and electrochemical measurements, and the biosensor step-by-step construction was characterized by electrochemical and spectroscopic techniques. As a proof of concept, the biosensor was used for the impedimetric detection of anti-SARS-CoV-2 Nucleocapsid protein monoclonal antibodies. The results showed a linear response for different antibody concentrations, good sensibility and possibility to quantify 7.442 and 0.4 ng mL -1 of monoclonal antibody for PPy in the globular and nanotubular morphology, respectively. The PPy-NTs biosensor was able to discriminate serum obtained from COVID-19 positive vs negative clinical samples and is a promising tool for COVID-19 immunodiagnostic, which can contribute to further studies concerning rapid, efficient, and reliable detections.

No abstract