Moisture-assisted post-annealing was performed on carbon-electrode based planar perovskite solar cells so as to improve the hole-extraction process. It was observed that, after being annealed at a relative humidity of 30% for 2 h, the short-circuit current density, fill factor, and open circuit voltage were all improved, leading to an improvement of 21.75% of power conversion efficiency [from 10.53 (±0.98)% to 12.82 (±1.07)%, with the optimized one at 14.77% for reverse scanning]. The transient photovoltage/photocurrent decay measurement and impedance spectroscopy study showed that, after being annealed at a relative humidity of 30%, the charge extraction rate was accelerated and charge transfer resistance was reduced, while recombination between photo-generated charges was retarded. Scanning electron microscopy studies indicated that voids were reduced between the perovskite film and the carbon electrode, which was ascribed to the re-coarsening process of the perovskite during the post-annealing process as revealed by the X-ray diffraction study. The improved contact accelerated hole-extraction between the perovskite film and the carbon electrode and then upgraded device performance.

There is an increasing need to synthesize biocompatible nanofibers with excellent mechanical and electrical performance for electrochemical and biomedical applications. Here we report a facile approach to prepare electroactive and flexible 3D nanostructured biomaterials with high performance based on bacterial cellulose (BC) nanofibers. Our approach can coat BC nanofibers with poly(3,4-ethylenedioxythiophene) (PEDOT) by in situ interfacial polymerization in a controllable manner. The PEDOT coating thickness is adjustable by the monomer concentration or reaction time during polymerization, producing nanofibers with a total diameter ranging from 30 to 200 nm. This fabrication process also provides a convenient method to tune different parameters such as the average pore size and electrical conductivity on the demands of actual applications. Our experiments have demonstrated that the 3D BC/PEDOT nanofibers exhibit high specific surface area, excellent mechanical properties, electroactive stability, and low cell cytotoxicity. With electrical stimulation, calcium imaging of PC12 neural cells on BC/PEDOT nanofibers has revealed a significant increase in the percentage of cells with higher action potentials, suggesting an enhanced capacitance effect of charge injection. As an attractive solution to the challenge of designing better electrode-cell interfaces, 3D BC/PEDOT nanofibers promise many important applications such as biosensing devices, smart drug delivery systems, and implantable electrodes for tissue engineering.

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By means of density functional theory, we perform a focused study of both body-centered-cubic (bcc) and face-centered-cubic (fcc) Fe-Ni random solid solutions, represented by special quasirandom structures. The whole concentration range and various magnetic configurations are considered. Excellent agreement on the concentration dependence of magnetization is found between our results and experimental data, except in the Invar region. Some locally antiferromagnetic fcc structures are proposed to approach experimental values of magnetization. Vibrational entropies of ordered and disordered systems are calculated for various concentrations, showing an overall good agreement with available experimental data. The vibrational entropy systematically contributes to stabilize disordered rather than ordered structures and is not negligible compared to the configurational entropy. Free energy of mixing is estimated by including the vibrational and ideal configurational entropies. From them, low-and intermediate-temperature Fe-Ni phase diagrams are constructed, showing a better agreement with experimental data than the one from a recent thermodynamic assessment for some phase boundaries below 700 K. The determined order-disorder transition temperatures for the L1 0 and L1 2 phases are in good agreement with the experimental values, suggesting an important contribution of vibrational entropy.